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LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

GIFT    OF 

J.PR.QF,  W.B.  Risiisra 

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From  the  collection  of  the 


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2006 


A  LABORATORY  OUTLINE  OF 
GENERAL  CHEMISTRY 


BY 

ALEXANDER  SMITH  B.Sc.,  PH.  D. 

ASSOCIATE  PROFESSOR  OF  CHEMISTRY  IN  THE  UNIVERSITY  OF  CHICAGO 


SECOND  EDITION       REVISED 


CHICAGO 

THE  UNIVERSITY  OF  CHICAGO  PRESS 
1902 


COPYRIGHT,  1899,  BY  ALEXANDER  SMITH 


Set  up  and  electrotyped  June,  1899 

Reprinted  September,  1900 
Second  Edition,  Revised,  October,  1902 


PREFACE  TO  THE  FIRST  EDITION. 

No  apology  is  offered  for  the  preparation  of  another  lab- 
oratory manual.  Each  teacher  of  chemistry  sooner  or  later 
catches  the  infection,  and  finds  himself  impelled  to  prepare 
an  outline  of  his  own.  There  is  little  material  that  is  orig- 
inal in  the  present  one.  The  author,  therefore,  acknowledges 
his  indebtedness  to  other  similar  outlines.  Ramsay's 
"  Experimental  Proofs  of  Chemical  Theory,"  may  be  named 
as  the  source  of  some  of  the  quantitative  experiments. 

In  selecting,  applying,  and,  to  a  slight  extent,  adding  to 
this  material,  several  considerations  have  been  kept  in  view, 
although  the  nature  of  the  case  has  made  it  easier  to  give 
effect  to  some  of  these  than  to  others. 

The  laboratory  work  is  most  emphatically  not  a  mechani- 
cal part  of  the  course,  in  which  the  use  of  the  intelligence  of 
the  student  plays  no  part  and  all  thought  is  reserved  for  the 
home  or  class-room.  It  is  an  essential  part  of  the  rigorous 
study  of  the  subject,  requiring  the  employment  of  the  head 
as  well  as  the  hands.  An  effort  has  therefore  been  made  to 
give  continuity  to  the  directions  by  the  form  in  which  they 
are  given,  and,  by  questions,  to  prepare  the  way  for  the  cor- 
relation of  the  facts  which  is  accomplished  in  quiz  and  lec- 
ture. This  does  not  mean  that  the  work  forms  by  itself  a 
complete  course  of  study  in  the  subject.  On  the  contrary, 
certain  important  topics,  such  as  Gay-Lussac's  "  Law  of  Vol- 
umes "  with  the  inferences,  based  on  Avogadro's  hypothesis, 
which  may  be  drawn  from  it,  can  more  fitly  be  illustrated  in 
the  lectures.  The  admirable  experiments  of  Hofmann  often 
involve  numerous  details  and  precautions  in  manipulation 
the  need  of  which  the  beginner  could  not  have  foreseen.  The 
apparatus  is  difficult  to  handle  on  the  first  trial  and  its  pro- 
vision involves  the  teacher  of  a  large  class  in  difficulties.  The 
significant  facts  to  be  observed  in  each  case  are  so  very  sim- 
ple as  not  absolutely  to  require  individual  experiment  for 

iii 

237477 


IV  PREFACE 

their  comprehension.  These  facts,  however,  demand  elabor- 
ate reasoning  for  the  development  of  their  significance,  and 
anything  like  spontaneous  application  by  the  pupil  is  very 
unlikely  to  occur.  Thus  the  difficulties  preceding  and  fol- 
lowing the  observation  of  the  central  fact  render  it  unsuitable 
for  illustration  in  the  laboratory.  On  the  other  hand,when  the 
practical  details  are  subordinated,  the  diagrammatic  nature 
of  these  experiments  renders  them  peculiarly  adapted  for 
lecture  purposes,  for  which,  in  fact,  they  were  originally 
designed.  Then,  too,  the  measurement  of  volume  appeals  to 
the  eye  more  directly  than  the  measurement  of  weight  and 
is,  therefore,  more  suitable  for  the  lecture  room.  The  meas- 
urement of  weight,  on  the  other  hand,  is  more  convincing 
when  carried  out  by  the  pupil  himself  and  is,  therefore,  bet- 
ter adapted  to  form  the  basis  of  the  majority  of  the  quanti- 
tative laboratory  experiments. 

Many  other  cases  of  the  omission  of  familiar  experiments, 
with  a  view  to  their  utilization  in  the  lecture,  will  be  noted. 

The  science  of  chemistry  deals  with  natural  phenomena 
themselves,  and  not  what  various  authors  have  said  about 
them.  It  is  the  part  which  the  pupil  can  learn  first-hand  in 
the  laboratory  by  observation  and  inference,  and  not  the 
part,  indispensable  though  it  is,  which  he  borrows  from  the 
book  or  teacher  which  will  correctly  shape  his  attitude  toward 
the  whole  science.  Much  opportunity  for  induction  has 
therefore  been  provided.  This  aspect  of  the  work  has  been 
emphasized  by  an  effort  to  discredit  reliance  on  books.  For 
this  purpose  experiments  with  easily  ascertainable  results, 
whose  course  nevertheless  cannot  be  anticipated  by  reference 
to  the  usual  run  of  text-books,  have  been  introduced  occa- 
sionally. Such  are  the  action  of  concentrated  sulphuric  acid 
on  ferrous  sulphide  (p.  57),  and  of  magnesium  on  nitric  acid 
(p.68). 

There  is  an  absurdity  inherent  in  the  usual  course  of 
directing  a  pupil  to  make  a  single  qualitative  experiment, 
with  haphazard  proportions  of  the  materials  and  other  con- 
ditions largely  selected  by  chance,  and  then  asking  him  to 
write  an  equation,  that  is,  to  draw  a  quantitative  conclusion. 


PREFACE  V 

The  pupil  feels  this  distinctly,  although  he  may  attribute  it 
to  the  wrong  cause It  is  not  always  convenient  to  fol- 
low quantitatively  every  feature,  even  in  one  of  these  selected 
chemical  changes,  but  some  features  may  be  investigated 
closely  in  one,  and  others  in  another,  with  a  resulting  synthe- 
sis of  the  whole  process  in  the  mind  of  the  pupil.  Thus  in 
the  burning  of  phosphorus  the  composition  of  the  pentoxide 
cannot  be  measured  by  the  beginner.  Again,  in  the  deter- 
mination of  the  combining  weight  of  iron  with  oxygen  (p.  16), 
the  action  of  the  nitric  acid  on  the  iron  and  the  effect  of  heat- 

ipg  the  nitrate  are  passed  over  to  avoid  premature  discussion 

of  the  properties  of  nitric  acid.  The  actions  of  carbon  on 
oxygen  (pp.  12  and  15),  and  of  zinc  on  hydrochloric  acid 
(pp.  17  and  18),  are  examples  of  the  more  complete  investiga- 
tion of  a  chemical  change. 

Even  in  cases  where  the  quantitative  aspect  is  deliberately 
left  to  be  supplied  by  the  book,  there  are  often  essential  fac- 
tors in  the  material  from  which  a  conclusion  is  to  be  drawn 
which  are,  at  the  time,  unknown  to  the  student  and  beyond  his 
observation.  Where  these  occur  a  direct  reference  to  the 
text-book  is  enjoined  by  inserting  an  R  in  parentheses  in  the 
directions.  Thus  in  Chap.  IV  (oxygen),  3  and  4,  the  inter- 
action of  certain  anhydrides  with  water,  the  solubilities  of 
nitrates,  chlorides  and  chlorates  of  potassium  and  silver,  etc., 
are  involved  in  the  understanding  of  the  chemical  changes 
observed.  This  sign  is  intended  to  enable  the  pupil  to  dis- 
tinguish when  he  is  expected  to  rely  on  himself  and  when  he 
must  seek  aid,  while  being  held  responsible  for  reaching  the 
correct  conclusion  in  either  case.  To  carry  out  this  idea, 
as  well  as  on  other  grounds,  a  few  volumes  for  reference 
(including  a  table  of  solubilities)  should  be  provided  in  the 
laboratory. 

Experiments  have  been  inserted  to  illustrate  such  theoret- 
ical matters  as  the  measurement  of  the  strength  of  acids  and 
phenomena  of  chemical  equilibrium,  ionic  equilibrium,  solu- 
tion tension,  etc.,  since  these  ideas  cannot  be  grasped  in  such 
a  way  as  ever  to  be  applied  unless  they  are  interwoven  with 
the  facts  they  explain.  Their  introduction  requires  no  justi- 


VI  PEEFACE 

fication.  Physical  chemistry  cannot  be  taught  in  the  first 
year  of  general  chemistry,  but  its  results  are  absolutely  indis- 
pensable to  a  rational  correlation  and  explanation  of  the  facts 
dealt  with  in  general  chemistry. 

In  Chaps.  I -IX,  which  form  one-third  of  the  year's  work, 
the  lectures  precede  the  laboratory  work,  while  not  covering 
altogether  the  same  ground.  In  this  way  the  beginner 
acquires  some  knowledge  of  the  nature  of  the  substances  he 
is  to  handle,  and  of  the  sort  of  results  he  is  to  look  for.  In 
Chaps.  X-XXV,  the  lectures  follow  the  laboratory  work  and 
the  latter  is  therefore  more  strictly  inductive  than  in  the 
earlier  chapters. 

The  work  outlined  is  designed  to  occupy  about  six  hours 
of  laboratory  work  per  week  for  nine  months,  on  the  assump- 
tion that  a  proportion  of  the  experiments  is  selected  for  omis- 
sion or  transference  to  the  lecture  room.  The  order  in  which 
the  elements  are  presented  and  the  period  at  which  quantita- 
tive work  is  introduced  may  readily  be  changed  as  circum- 
stances demand. 

College  students  who  have  already  completed  a  year  of 
chemistry  in  a  secondary  school  will  naturally  have  performed 
many  of  the  experiments  here  given,  and  have  learned  all 
they  can  teach.  A  selection,  by  way  of  suggesting  a  basis 
for  a  college  course  in  continuation  of  school  work  for  such 
students,  is  printed  in  the  Appendix 

I  have  to  thank  Professor  J.  B.  Garner  (Wabash  College), 
and  Dr.  H.  N.  McCoy  (of  this  department)  for  many  valuable 
suggestions.  I  owe  to  the  latter  also  the  admirable  working 
out  of  the  details  of  the  quantitative  experiments  on  the  com- 
position of  carbon  dioxide  (p.  15),  on  the  proportions  of  cop- 
per to  oxygen  in  the  two  oxides  (p.  19),  on  the  combining 
weight  of  iron  (p.  16),  and  on  the  estimation  of  the  activity 
of  an  acid  (p.  64),  as  well  as  the  realistic  arrangement  for 
making  sulphuric  acid  from  pyrite  (p.  59).  Finally  I  have 
to  express  my  indebtedness  to  Miss  Carol  Paddock  for  pre- 
paring the  illustrations. 

Chicago,  May,  1899.  ALEXANDER  SMITH. 


PREFACE  TO  THE  SECOND  EDITION. 

In  preparing  this  edition  the  plan  of  the  former  one  has 
been  preserved  and  its  application  has  been  made  more 
thoroughgoing.  An  almost  entirely  new  set  of  figures,  some 
new  experiments,  and  innumerable  alterations  in  the  wording 
of  the  directions  and  the  questions  have  been  introduced. 
The  chief  objects  in  view  have  been  to  secure  a  more  logical 
presentation  of  the  subject  and  to  make  the  student  less 
dependent  on  help  from  the  instructors. 

The  experiments  have  also  been  adapted  more  closely  to 
the  set  of  apparatus  in  the  possession  of  each  student. 
Except  in  cases  of  breakage,  it  should  not  now  be  necessary 
for  him  to  visit  the  storeroom  more  than  a  dozen  times  in 
the  course  of  the  whole  year. 

VFhe  teacher  will  find  it  a  great  help  to  furnish  his  stu- 
derils  with  a  carefully  compiled  list  of  references,  using 
books  in  his  particular  laboratory.  Without  this  much  time 
may  be  wasted  through  ignorance  of  where  to  look  for  the 
material  required  in  answering  questions  to  which  an  [R]  is 
appended. 

As  some  of  the  opinions  expressed  in  the  preface  to  the 
first  edition  have  since  appeared  in  expanded  form  in  The 
Teaching  of  Chemistry  and  Physics,  written  by  the  author 
in  collaboration  with  Professor  E.  H.  Hall,  this  preface  has 
not  been  reprinted  in  full.  The  presence  of  most. of  it,  how- 
ever, seemed  to  be  called  for  in  explanation  of  certain  fea- 
tures of  the  present  book. 

Chicago,  October,  1902.  A.  S. 


vii 


CONTENTS. 

CHAPTERS  PAGES 

I.  APPARATUS  1 
II.  PHYSICAL  PROPERTIES  6 
III.  CHARACTERISTICS  OP  CHEMICAL  CHANGE  8 
IV.  OXYGEN  11 
V.  EQUIVALENT  WEIGHTS,  FORMULAE,  AND  EQUATIONS  15 
VI.  HYDROGEN  22 
VII.  WATER  AND  SOLUTION  26 
VIII.  CHLORINE  AND  HYDROGEN  CHLORIDE  30 
IX.  THE  ATMOSPHERE,  NITROGEN,  AND  AMMONIA   -  -    34 
X.  BROMINE,  IODINE,  AND  FLUORINE,  AND  THEIR  COM- 
POUNDS WITH  HYDROGEN  37 
XI.  OXYGEN  COMPOUNDS  OF  THE  HALOGENS.    OZONE  AND 

HYDROGEN  PEROXIDE  43 
XII.  IONIC  CHEMICAL  ACTIONS.     INTERACTIONS  OF  ACIDS, 

BASES  AND  SALTS  46 

XIII.  SULPHUR  AND  ITS  COMPOUNDS  56 

XIV.  THE  ACTIVITY  OF  ACIDS  MEASURED  CHEMICALLY  64 
XV.  OXIDES  AND  OXYGEN  ACIDS  OF  NITROGEN  66 

XVI.  PHOSPHORUS,  ARSENIC,  ANTIMONY,  BISMUTH  71 

XVII.  CARBON  76 

XVIII.  SILICON  AND  BORON  81 

XIX.  METALS  OF  THE  ALKALIES  83 

XX.  METALS  OF  THE  ALKALINE  EARTHS  89 

XXI.  COPPER  AND  SILVER  -    92 

XXII.  MAGNESIUM,  ZINC,  CADMIUM,  MERCURY  95 

XXIII.  ALUMINIUM,  TIN,  LEAD  98 

XXIV.  CHROMIUM,  MANGANESE  101 
XXV.  IRON,  COBALT,  NICKEL  -  104 

APPENDIX          - 106 


GENERAL  INSTRUCTIONS. 

Check  your  apparatus  by  comparison  with  list,  have  deficien- 
cies made  good  at  the  storeroom,  obtain  the  key  of  a  locker 
in  the  hall,  enter  the  numbers  of  this  and  the  desk  keys  on 
the  list,  and  then  sign  and  return  the  list  to  the  storekeeper. 

Read  the  "  Regulations  "  posted  in  the  laboratory. 

Provide  yourself  with  a  notebook  and  make  a  careful 
permanent  record  immediately  after  each  experiment.  Enter 
the  numbers  of  the  chapters  and  paragraphs  of  the  outline 
systematically,  so  as  to  save  the  necessity  of  copying  the 
directions,  and  place  the  same  numbers  at  the  head  of  each 
page  in  the  notebook.  State  (1)  what  you  did,  if  anything 
beyond  the  directions,  (2)  what  you  observed,  (3)  what  conclu- 
sions you  drew.  A  sketch  of  the  apparatus  will  enable  you 
to  recall  the  circumstances  of  the  experiment,  if  later  refer- 
ence to  it  is  necessary. 

The  blank  pages  are  not  intended  for  the  final  notes.  They 
may  be  used  for  individual  suggestions  given  by  the  instruc- 
tor, preliminary  notes,  record  of  weighings,  etc. 

Whenever  an  interrogation  point  (?)  or  a  direct  question 
appears,  a  corresponding  note  should  appear  in  the  notebook. 

The  very  numerous  questions  asked  in  the  course  of  this 
outline  are  intended  to  be  answered,  not  by  speculation,  but 
by  careful  observation,  and  reasoning  based  on  the  results  of 
this.  In  many  cases  the  student  will  find  it  necessary  to 
devise  and  carry  out  further  experiments  of  his  own  before  a 
satisfactory  answer  is  obtained.  In  some  more  complex  cases, 
where  much  time  and  work  would  be  necessary,  the  books 
set  apart  for  reference  are  to  be  consulted.  An  [R]  indicates 
such  necessity.  This  should  be  done,  however,  only  after 
the  experiments  have  been  made  and  the  notes  written  up  as 
far  as  possible. 

The  directions  have  been  expressed  with  the  utmost  care 
and  brevity.  Every  word  is  significant.  Italics  are  therefore 
nowhere  employed. 

The  equation  should  always  be  given  in  the  notes  when  a 
chemical  change  has  been  observed,  but  an  equation  alone  is 
never  a  sufficient  record. 

Where  the  word  [Instructions]  appears,  consult  the  instruc- 
tor before  going  further. 

In  experiments  marked  [Quant.]  use  the  finer  balance,  in 
all  other  cases  the  rough  scales  in  the  laboratory. 

xi 


Xll  GENERAL    INSTRUCTIONS 

The  expression  [Temp,  order]  indicates  that  the  necessary 
apparatus  must  be  obtained  from  the  storeroom  on  a  tempo- 
rary order. 

Where  exact  quantities  are  not  indicated,  very  small 
amounts  of  solutions  (1  c.c.  or  less)  should  be  taken.  This 
advice  is  given,  partly  to  secure  saving  of  material,  but  chiefly 
to  avoid  the  waste  of  time  which  working  with  large  quanti- 
ties always  entails. 

To  obtain  the  necessary  chemical  substances,  do  not  carry 
the  bottles  from  the  side-shelf  to  the  desk.  Bring  a  clean 
test-tube  for  liquids  and  a  watch  glass  for  solids.  For  the 
latter  a  piece  of  the  paper  provided  near  the  side-shelf  may 
also  be  used.  When  too  much  of  any  reagent  has  been  taken 
do  not  return  it  to  the  bottle. 

The  chemicals  are  divided  into  three  sets,  each  arranged 
alphabetically  according  to  the  scientific  names.  The  first  set 
consists  of  solids  in  small  bottles,  the  second  of  the  solids 
which  are  needed  in  greater  quantities  in  large  bottle,  the 
third  of  liquids.  The  bottles  and  their  places  are  numbered 
consecutively  to  facilitate  accurate  replacement,  and  scrupu- 
lous care  must  be  taken  not  to  disarrange  them.  Read  the 
labels  attentively,  as  there  are  frequently  several  kinds  of  the 
same  substance  (e.  g.,  pure  and  commercial,  dilute,  concen- 
trated, and  normal).  For  some  experiments  solutions  of 
special  concentrations  have  to  be  made  by  the  student. 

All  materials  are  supplied  through  the  storeroom  service. 
Do  not  therefore  take  side-shelf  bottles,  when  found  empty, 
to  the  instructor,  but  to  the  storekeeper  for  re-filling. 

The  nine  bottles  on  the  desk  contain  aqueous  solutions  of 
sodium  hydroxide,  sodium  carbonate,  and  ammonium  hydrox- 
ide, which  are  not  to  be  found  on  the  side-shelves,  and  sul- 
phuric, hydrochloric,  and  nitric  acids  in  concentrated  and 
dilute  form.  These  acids  are  all  commercial.  The  corres- 
ponding pure  concentrated  and  dilute  acids  will  be  found  on 
the  side-shelf  and  are  to  be  used  only  when  the  outline  so 
directs. 

All  students  must  work  independently  except  were  co- 
operation of  two  students  is  expressly  directed, 


CHAPTER  I. 

APPARATUS. 

1.  INSTRUCTIONS. 

a.  Read  the  general  instructions  preceding  this  chapter 
very  carefully,  and  do  not  fail  to  observe  them. 

b.  The  number  of  blast-lamps  and  balances  being  limited, 
the  whole  class  cannot  perform  the  experiments  in  this  chap- 
ter simultaneously  in  the  order  given.    Two  students  from 
the  group  under  each  assistant,  as  soon  as  they  have  checked 
their  list  of  apparatus,  will  be  sent  to  the  blast -lamp  table  to 
carry  out  2  under  the  direction  of  a  special  assistant.    Two 
others  will  pass  to  5  and  6,  returning  to  2,  3,  or  4  when  these 
are  accomplished.    The  remainder  of  each  section  will  be 
sent  as  early  as  possible  in  pairs  to  take  the  places  of  those 
returning    from  glass-blowing  (2)  and  weighing    (6),  and 
meanwhile  will  occupy  themselves  with  3,  4,  and  5,  or  work 
in  Chap.  III. 

c.  Chap.  II  is  intended  for  those  only  whose  preparation 
in  physics  is  defective.     It  is  therefore  to  be  omitted,  except 
in  cases  where  personal  instructions  to  the  contrary  are  given. 

d.  No  record  of  1,  2,  and  3  is  required  in  the  note-book. 

2.  GLASS-BLOWING  [Instructions  and  notes  below]. 

a.  Cut  a  small  piece  off  the  wide  glass  tubing. 

b.  Make  a  test-tube  of  soft  glass. 

c.  Make  a  test-tube  of  hard  glass. 

d.  Connect  two  pieces  of  narrow  glass  tubing  to  make  a 
longer  piece. 

Notes. — Always  round  off  the  edges  of  glass  tubing  by  soften- 
ing in  the  Bunsen  flame.  In  the  case  of  test-tubes,  and  other 
tubes  of  wide  bore  in  which  corks  are  to  be  inserted,  use  a 
pointed  piece  of  charcoal  or  a  file  for  spreading  the  mouth. 
Always  distend  softened  parts  by  blowing  and  then  cover  with 
soot  in  the  luminous  flame  before  allowing  finally  to  cool,  other- 
wise cracks  will  appear. 

In  bending  glass  tubes,  always  use  an  ordinary  flat  luminous 
flame,  and  hold  the  tubing  lengthwise  in  the  flame.  Never 
employ  the  Bunsen  flame.  Discover  the  reason  for  this  injunc- 
tion by  bending  a  tube  in  the  Bunsen  flame  and  comparing  the 
result  with  the  bend  made  in  the  proper  way  (?).  Do  not  bend 
while  the  tube  is  in  the  flame,  but  after  removal  (why?). 


APPARATUS 


3.  CONSTRUCTION  OF  A  WASH  BOTTLE.  Select  a  good  cork 
and  soften  it  by  means  of  the  cork  press.  Bore  two  holes 
with  a  cork  borer  [See  note  below]  and  smooth  them  with  a 
file.  Prepare  two  glass  tubes  as  in  Fig.  1  [See  note  on  bend- 
ing under  2,  d  above], 
round  their  edges, 
and  insert  them. 
Make  the  nozzle  by 
softening  a  piece  of 
glass  tubing  in  the 
Bunsen  flame,  draw- 
ing it  to  capillary 
dimensions,  and  cut- 
ting. Connect  it  by 
means  of  a  short 
'piece  of  rubber  tub- 
ing [Storeroom].  Test 


Fig.  1. 


the  apparatus  to  see  that  the  joints  are  air-tight  [Instructions]. 
Fill  the  bottle  with  distilled  water.  (Distilled  water  is  used 
for  nearly  all  experiments,  and  for  rinsing  glassware.) 

Notes. —  The  cork  borer  is  made  of  brass,  and  the  edge  is 
easily  turned.  JForm  the  habit  of  examining  the  edge  and  fresh- 
ening it  by  cautious  application  of  a  file  [Instructions]  before  use. 
Do  not  hold  the  cork  against  the  table  while  boring,  as  the  edge 
of  the  tool  may  be  ruined.  Hold  the  cork  in  the  hand  and  bore 
from  the  narrow  end  with  care,  exactly  parallel  to  the  axis.  If 
the  cork  and  borer  are  rotated  round  their  axes  and  the  edge  is 
fresh,  very  little  force  will  be  required. 

To  avoid  waste  of  corks,  and  of  time  in  boring  fresh  ones,  the 
thermometer,  the  stems  of  the  dropping-funnel  and  thistle-tube, 
and  the  ordinary  glass  tubing  furnished  are  all  of  the  same 
diameter. 

4.  BUNSEN  BURNER. 

a.  Notice  the  effect  of  opening  and  closing  the  holes  at 
the  bottom  of  the  tube.  What  is  the  proximate  cause  of  the 
difference  in  the  flames  ?  In  using  the  burner,  always  adjust 
the  ring  so  as  to  get  a  noiseless,  non-luminous  flame. 

6.  Notice  the  structure  of  each  flame.  Determine  which 
parts  are  relatively  hotter  and  which  cooler  by  placing  a 
match  and  a  piece  of  platinum  wire  across  the  flame  in  various 
parts  and  by  causing  the  flame  to  impinge  on  a  sheet  of  paper 
spread  flat  on  the  table.  Make  sketches  showing  the  real 
form  of  the  flame.  Where  would  you  hold  an  object  in  the 
non-luminous  flame  in  order  to  get  the  greatest  heating 
effect  ?  Which  region  will  be  deficient  in  oxygen  and  which 
will  have  excess  ?  Name  those  regions  [R]. 


APPARATUS  8 

c.  Fuse  the  end  of  a  piece  of  glass  rod  (75  mm.  long)  in 
the  blast-lamp  and  insert  a  short   piece  of  platinum  wire 
[Storeroom].     Make  a  bead  of  borax  [See  note  below]  on  the 
straight   wire  (make  no   loop   at  the  end),  using  the  non- 
luminous  flame.    Observe  the  behavior  of  the  borax  and  ex- 
plain |H].    The  borax  is  picked  up  by  touching  it  with  the 
heated  wire.   The  bead  must  be  small  to  avoid  its  dropping  off. 

d.  Dissolve  a  speck  of  manganese  dioxide  in  the  bead  by 
heating  in  the  oxidizing  part  of  the  flame,  and  observe  the 
color  of  the  bead.     If  the  bead  is  opaque,  too  much  of  the 
dioxide  has  been  taken:    throw  the  molten  bead  off  and 
start  again. 

e.  Heat  this  bead  in  the  reducing  part  of  the  flame  (?).  To 
get  the  best  result,  lower  the  flame  until  it  is  about  6  cm. 
high,  close  the  holes  until  a  speck  of  luminosity  appears  at 
the  apex  of  the  inner  cone,  and  hold  the  bead  steadily  in  that 
spot.    Before  withdrawing  the  bead,  lower  it  into  the  gas  in 
the  inner  cone  to  cool. 

/.  In  the  oxidizing  part  of  the  flame  again  ( ?). 

Notes. — There  are  six  bottles  on  your  desk,  containing  three 
acids  in  dilute  and  concentrated  form.  These  are  not  pure,  and 
should  be  used  wherever  the  employment  of  pure  acids  [Side- 
shelf]  is  not  explicitly  enjoined.  The  three  other  bottles  contain 
solutions  of  sodium  carbonate,  and  sodium  and  ammonium 
hydroxides,  which  are  not  to  be  found  on  the  side-shelf. 

The  chemicals  upon  the  side-shelf  are  arranged  alphabetically, 
according  to  the  scientific  names,  in  three  sets :  first,  solids  in 
small  bottles  ;  second,  solids  in  large  bottles  ;  third,  solutions  and 
liquids.  The  whole  side-shelf  outfit  is  numbered  consecutively, 
to  secure  easy  return  of  each  bottle  to  its  own  place.  For 
example,  borax  is  in  bottle  No.  117,  labeled  sodium  tetraborate. 
Do  not  remove  the  bottles  to  your  desk.  Fetch  the  material  in  a 
watch  glass,  piece  of  paper,  or  clean  test-tube. 

5.  MEASURING  VESSELS. 

a.  Fit  a  burette  with  a  short  piece  of  rubber  tubing  and 
nozzle  (Fig.  2).     The  exit  may  be  closed  either  by  means  of 
a  pinch  clamp  or  by  placing  a  small  piece  of  glass  rod  in  the 
middle  of  the  rubber  tube  to  choke  the  bore.     In  the  latter 
case,  pinching  the  tube  surrounding  the  rod  will  permit  the 
liquid  to  flow  at  any  desired  rate  from  the  nozzle. 

b.  Fill  the  burette  with  distilled  water,  taking  care  that 
the  air  below  the   clamp  and  in   the  nozzle  is  completely 
expelled.     Read  the   height   of    the   water  in   the  burette, 
observing  the  lower  side  of  the  meniscus  and  estimating 
tenths  of  a  division. 

Measure  10  c.c.  of  distilled  water  into  each  of  two  test- 


4  APPARATUS 

tubes,  the  first  with  a  graduated  cylinder,  the  other  with  the 
burette.  Which  gives  the  more  accurate  measurement,  and 
why  ?  Sketch  one  test-tube  with  contents  full  size. 


c.  Measure  by  means  of  the  cylinder  the  volumes  of 
water  your  flasks  and  beakers  hold,  and  record  the  figures. 
Fill  them  to  a  convenient  height  for  use,  and  not  to  the  brim. 

6,  USE  OF  THE  SIMPLE  BALANCE  [Instructions ;  Quant.]. 

a.  Allow  the  beam  of  the  balance  to  swing,  and  observe 
whether  the  pointer  makes  equal  excursions  on  each  side  of 
the  zero  point.  If  it  does  not,  correct  the  defect  by  placing 
small  pieces  of  paper  in  one  pan.  In  weighing  any  object, 
weights  are  added  in  the  other  pan  until  the  vibrations  of  the 
pointer  on  each  side  are  equal  (not  by  bringing  the  beam  to 
rest !). 

Place  a  10  g.  weight  in  each  pan,  equalize  the  vibrations 
as  above,  add  the  .01  g.  weight  to  the  right-hand  pan,  and 


APPARATUS  5 

find  the  reading  about  which  the  pointer  now  oscillates.  This 
gives  the  deflection  for  .01  g.  and  may  be  used  for  estimating 
weights  less  than  .01  g. 

Notes. —  Great  care  must  be  taken  not  to  injure  the  balance 
or  the  weights.  The  pans  of  the  former  must  be  let  down  every 
time  weights  or  other  objects  are  added  or  removed.  Objects  to 
be  placed  on  the  pans  must  be  carefully  cleaned  and  dried.  Solids 
to  be  weighed  must  be  placed  on  a  piece  of  glazed  paper,  or  a 
watch  glass,  never  on  the  pan  directly.  The  weights  must  be 
lifted  by  means  of  the  forceps,  not  by  the  hand.  If  the  weights 
are  touched  by  the  hand,  they  oxidize  rapidly  and  become  inexact. 
In  reckoning,  count  first  by  the  places  vacant  in  the  box  and 
check  by  counting  the  weights  themselves.  This  will  enable  you 
to  avoid  the  commonest  error  in  weighing.  Finally,  record  the 
weights  in  the  note-book  or  laboratory  outline,  and  never  on  loose 
sheets  of  paper.  Loss  of  the  latter,  which  is  almost  sure  to  occur, 
destroys  the  whole  experiment,  which  may  have  occupied  hours 
of  time. 

b.  Ascertain  the  weight  of  a  small  dry  beaker.  Measure 
into  it  a  quantity  of  water  (about  10  c.c.)  from  the  burette  and 
weigh  again  [See  note  below]. 

In  making  any  one  of  the  readings  of  the  burette,  endeavor, 
by  altering  the  level  of  the  eye,  to  estimate  what  error  might 
unconsciously  be  made.  Note  this  in  c.c.  and  express  it  in 
per  cent,  of  the  volume  being  measured  when  the  reading  was 
made. 

Note. — Wherever  in  this  outline  instructions  like  the  above 
are  given,  do  not  attempt  to  take  the  exact  amount  specified,  but 
ascertain  exactly  how  much  has  been  taken.  A  quantity  is  indi- 
cated because  one  approximating  that  named  will  be  most  con- 
venient for  the  apparatus  and  for  securing  the  object  in  view. 


CHAPTER  II. 

PHYSICAL    PROPERTIES. 

1.  SPECIFIC  GRAVITY  [Quant.]. 

a.  Calculate  from  the  above  result  (Chap.  I,  6,  b)  the  spe- 
cific gravity  of  water  (weight  of  1  c.c.).     Criticise  the  result. 
Repeat  the  measurement  and  calculation  with  the  solution  of 
sodium  carbonate  on  your  desk,  and  with  chloroform.     Dry 
the  burette  before  filling  with  chloroform.     Be  careful  not  to 
let  these  or  any  liquids  reach  the  pan  of  the  balance. 

b.  Suspend  a  piece  of  thread  from  the  hook  above  the  pan 
of  the  balance  and  adjust  as  above  until  the  pointer  makes 
equal  excursions  on  each  side  of  the  zero  point.    Tie  to  the 
thread  a  short  piece  of  thick  glass  rod  and  weigh  first  in  air, 
then  in  water.     Calculate  the  specific  gravity  of  glass. 

Note. —  Use  the  shelf  of  your  pneumatic  trough  as  a  bridge 
on  which  to  support  the  beaker  of  water  over  the  pan. 

c.  Make  a  mark  with  your  file  in  the  middle  of  the  neck 
of  a  flask  holding  about  25  c.c.,  fill  with  distilled  water  to  the 
mark,  and  weigh.    Weigh  some  small  pieces  of  sulphur  (about 
2  g.),  put  them  into  the  flask,  bring  the  level  of  the  water  to 
the  mark  again,  and  wsigh  once  more.     Calculate  the  specific 
gravity  of  sulphur. 

2.  CHARLES'S  LAW  [Quant.]. 

Take  a  dry  flask  [Instructions]  of  300  c.c.  capacity  and  fit 
with  a  rubber  stopper,  short  pieces  of  glass  and  rubber 
tubing,  and  clip,  as  in  Fig.  3.  Find  the  weight  of  the 
flask  as  thus  fitted  (w).  Make  a  mark  on  the  neck  of 
the  flask  at  the  bottom  of  the  stopper,  and  always 
insert  the  latter  the  same  distance.  Place  the  flask 
vertically  in  a  pot  of  boiling  water  so  that  it  is 
immersed  completely,  holding  it  in  position  by 
means  of  a  universal  clamp,  and  open  the  clip. 
After  several  minutes  close  the  clip,  remove  the  flask, 
invert  it  in  a  pneumatic  trough  filled  with  water, 
Fig.  3.  open  the  clip  to  allow  the  water  to  enter,  equalize 
the  level  inside  and  out,  close  the  clip,  dry  the  outside  of  the 
flask  carefully  and  weigh  (a).  Fill  the  flask  and  tube  com- 
pletely with  water  and  weigh  again  (&).  Take  the  temperature 
of  the  water  in  the  trough  (£),  and  of  the  boiling  water  (£1). 


PHYSICAL    PROPERTIES  7 

Subtracting  the  weight  of  the  flask  (w)  from  (a)  gives  the 
volume  of  water  which  entered  (1  gr.=  1  c.c.).  Subtracting 
the  weight  of  the  flask  from  (6)  gives  the  total  volume  of  the 
flask.  Subtracting  these  two  differences,  we  get  the  volume 
of  air  which  partially  filled  the  flask  at  £°,  and  completely  at 
ti°.  The  difference  between  t°  and  t^  gives  the  change  in 
temperature.  Calculate  the  expansion  (in  c.c.)  of  1  c.c.  heated 
fromtf0  to  t°  -f  1°.  Express  this  as  a  common  fraction.  What 
is  the  theoretical  result  calculated  from  Charles's  law? 

The  result  is  the  same  whatever  gas  or  mixture  of  gases 
is  taken.  (Exceptions,  K?) 

3.  BOYLE'S  LAW  [Quant.]. 

Take  a  T  tube  [Temp,  order]  and  connect  one  of  the  short 
arms  with  the  apparatus  used  in  the  last  experiment.  (The 
flask  must  be  dry  as  before.)  Close  the  other  short  limb  with 
a  piece  of  rubber  tubing  and  another  clip.  Immerse  the  long 
(40  cm.)  limb  in  a  beaker  of  mercury.  Open  both  clips  and 
exhaust  the  air  as  far  as  possible  by  sucking.  Close  the  clips 
and  measure  the  height  of  the  mercury  in  the  tube.  Discon- 
nect the  T  tube,  leaving  the  clip  on  the  flask  closed.  Open 
this  under  water,  equalize  the  levels,  close  the  clip,  and  weigh. 
Ascertain  the  height  of  the  barometer  (p). 

Subtracting  the  weight  of  the  flask  (known)  from  the 
above  weight  gives  the  volume  of  water  which  entered.  Sub- 
tracting this  volume  from  the  known  total  volume  (d\  we  get 
the  volume  (c)  of  the  air  which  partially  filled  the  flask  at 
atmospheric  pressure  (p)  and  completely  at  the  reduced  press- 
ure (p1).  Get  (p1)  by  subtracting  the  height  of  the  mercury 
from  (p). 

Boyle's  law  states  that  c:d:ip':p.  Calculate  (d)  from  (c), 
(p'\  and  (p)  by  this  formula  and  compare  with  the  value  of 
(d)  observed. 


CHAPTER  III. 

CHARACTERISTICS  OF  CHEMICAL  CHANGE. 

1.  QUALITATIVE  STUDY  OF  CHEMICAL  CHANGE. 

a.  Fit  up  an  aspirator,  attach  it  to  a  piece  of  hard  glass 
tubing  25-30  cm.  long,  close  the  other  extremity  of  this  with  a 
stopper  fitted  with  glass  tube,  rubber  tube,  and  clamp,  and 
provide  the  other  tubes  and  beaker  all  as  shown  in  Fig.  4. 
The  stopper  of  the  aspirator  should  be  of  rubber.  Support 


Fig.  4. 


the  hard  glass  tube  at  its  outer  end  by  means  of  a  clamp 
attached  to  the  iron  stand.  Test  the  apparatus  and  see  that 
it  is  perfectly  air-tight  before  proceeding  further.  To  do  this, 
place  an  inch  or  two  of  water  in  the  bottle,  close  the  apparatus, 
and  blow  a  little  air  into  the  bottle  through  the  overflow  tube. 
If  now  the  water  remains  steadily  at  an  elevated  point  in  the 
long  tube  there  is  no  leak ;  if  it  recedes,  the  joints  must  be 
re-examined  and  made  tight.  Fill  the  porcelain  boat  with 
powdered  iron,  which  should  be  dried  previously  by  heating 
it  gently  in  a  test-tube,  and,  using  the  rough  scales,  ascertain 
the  gross  weight  of  boat  and  iron.  [This  experiment  is  not 
"  quantitative."]  Examine  the  physical  properties  of  the  iron 
and  note  the  results.  Place  the  boat  in  the  middle  of  the 
tube.  Fill  the  aspirator  to  the  neck  with  water  and  put  the 

8 


CHARACTERISTICS  OF  CHEMICAL  CHANGE       9 

tubes  in  position,  without,  however,  finally  inserting  the  stop- 
per. Displace  the  air  in  the  hard  glass  tube  with  a  gentle 
stream  of  oxygen  from  the  cylinder  of  compressed  oxygen, 
and  then  press  the  stopper  home  and  pass  in  more  oxygen 
until  half  of  the  water  has  been  driven  over  into  the  large 
beaker  placed  to  receive  it.  Turn  off  the  oxygen  and  close 
the  spring  clamp  behind  the  hard  glass  tube.  The  object  of 
this  whole  operation  is  to  expel  nearly  all  the  air  and  to  fill 
the  apparatus  with  a  volume  of  confined  oxygen.  Any  subse- 
quent change  in  this  volume  of  oxygen  will  be  accompanied 
by  the  entrance  or  exit  of  water  through  the  rubber  tube  and 
nozzle.  To  record  the  amount  of  oxygen  at  starting,  leave 
the  overflow  beaker  full  of  water,  move  it  up  or  down  until 
the  levels  of  the  water  in  the  bottle  and  beaker  are  the  same 
(why?),  and  stick  a  small  strip  of  wet  paper  on  the  outside  of 
the  bottle  to  mark  the  height  of  the  water. 

Now  heat  the  iron,  at  first  gently,  and  then  strongly  [See 
note]  with  the  Bunsen  flame,  noticing  all  that  happens.  If 
the  volume  of  the  oxygen  changes,  continue  the  operation 
till  no  further  change  occurs.  Finally,  when  the  tube  has 
cooled,  mark  the  level  of  the  water  again  in  the  same  manner 
as  before  and  then  weigh  the  boat  and  contents,  and  examine 
the  latter.  Which  of  the  characteristics  of  chemical  change 
were  observable? 

Note. —  A  piece  of  wire  gauze  bent  in  cylindrical  form  and 

E  laced  round  the  part  of  the  hard  glass  tube  which  is  to  be 
eated  will  diminish  the  risk  of  cracking  and  may  be  used  in 
this  and  all  subsequent  experiments  of  the  same  nature. 

b.  Gunpowder  is  made  from  niter  (potassium  nitrate),  roll 
sulphur,  and  charcoal.  Bring  specimens  of  these  substances 
from  the  side-shelf  on  watch  glasses,  and  examine  them  as 
regards  properties  which  could  be  used  for  separation  and 
recognition  [R.,  Lect.].  The  solubility  of  each  in  water  and 
carbon  disulphide  will  be  most  useful  for  the  former.  Ex- 
amine some  gunpowder,  from  the  side-shelf.  Does  it 
resemble  the  constituents  physically?  Devise  a  method  of 
ascertaining  whether  it  is  still  a  mixture  of  these  substances, 
or  has  changed  chemically  during  manufacture.  Try  your 
method  (?). 

Notes. —  Pour  away  all  ill-smelling  substances,  like  carbon 
disulphide,  in  the  sink  in  the  hood  and  not  in  the  ordinary  sinks 
or  jars. 

In  filtering,  always  cut  the  paper  to  circular  form  with  scis- 
sors and,  to  avoid  loss  of  any  of  the  liquid,  use  as  small  a  paper 
and  funnel  as  will  serve  the  purpose.  Never  allow  the  paper  to 
project  above  the  edge  of  the  funnel.  It  should  not  come  within  less 
than  one-quarter  of  an  inch  of  the  top  of  the  latter  (cf.  Fig.  13). 


10  CHARACTERISTICS   OF    CHEMICAL    CHANGE 

2.  LAW  OF  DEFINITE  PROPORTIONS  [Quant.,  *.  e.,  use  finer 
balance  and  weigh  to  nearest  cgm.]. 

a.  Prepare  two    burettes    and    two    evaporating-dishes. 
Weigh  an  evaporating-dish.    Dilute  25  c.c.  of  pure  [Side-shelf] 
concentrated  hydrochloric  acid  [See  note  below]  with  an  equal 
volume  of  water,  and  fill  a  burette  with  it.    Fill  the  second 
burette  with  ammonium  hydroxide  solution  [On  desk].    From 
the  first  burette  run  5  c.c.  of  the  acid  into  the  dish  and  add 
litmus  solution  until  the  liquid  shows  a  distinct  pink  tinge. 

Read  the  burette  containing  the  ammo- 
nium hydroxide  and  run  the  solution 
into  the  acid,  drop  by  drop  (stirring 
constantly),  until  the  exact  point  is 
reached  at  which  the  tint  of  the  litmus 
is  halfway  between  red  and  blue. 
Evaporate  [Hood]  the  solution  to  com- 
plete dryness  on  the  steam  bath,  cool,  and 

find  the  weight  of  the  ammonium  chloride  produced.  When,  as 
in  this  case,  no  disagreeable  fumes  are  given  off,  it  is  better  to 
use  a  beaker  of  boiling  water  on  the  desk  instead  of  the  steam 
bath.  After  weighing,  heat  once  more  for  half  an  hour  and  weigh 
again  to  ascertain  whether  the  residue  was  completely  dry.  This 
precaution  is  taken  in  all  experiments  of  this  kind.  The  naked 
flame  may  not  be  used,  as  the  ammonium  chloride  is  volatile. 
Weigh  the  second  evaporating-dish,  take  5  c.c.  of  hydro- 
chloric acid  as  before,  and  add  twice  the  volume  of  ammonium 
hydroxide  used  in  the  previous  experiment.  Evaporate 
[Hood]  and  weigh  as  before. 

Compare  the  amounts  of  ammonium  chloride  found  in  the 
two  experiments  and  interpret  the  result. 

b.  Carefully  weigh  an  evaporating-dish  and  weigh  out 
into  it  about  1  g.  [See  note,  p.  3,  6,  6J  of  sodium  hydrogen 
carbonate.     Dissolve  in  pure  dilute  hydrochloric  acid,  adding 
little  by  little  and  covering  with  a  watch  glass  between  suc- 
cessive additions  to  avoid  loss  by  spirting.     When  the  solid 
has  wholly  dissolved,  wash  the  watch  glass  over  the  dish,  and 
evaporate  [Hood]  the  contents  of  the  latter  on  the  steam  bath, 
or  on  a  beaker  of  boiling  water.     Allow  the  dish  to  cool,  and 
weigh.     To  make  sure  that  the  drying  was  complete,  heat  for 
half  an  hour  or  more  and  weigh  again.     Calculate  the  ratio 
by  weight  of  the  carbonate  taken  to  the  salt  produced,  1  :  x. 

Repeat  the  experiment,  using  about  two  grams  of  the  car- 
bonate, and  find  the  ratio.  Compare  the  ratios  and  interpret. 

A  small  flask  is  very  convenient  for  the  action  of  the  acid 
on  the  carbonate,  and  the  contents  can  afterward  be  rinsed 
into  an  evaporating-dish. 


CHAPTER  IV. 

OXYGEN. 

1.  SOURCES.    Heat  small  quantities  of  barium  peroxide, 
lead  dioxide,  potassium  dichromate,  and  manganese  dioxide 
(dry  this  before  use  by  heating  it  for  a  few  minutes  in  a 
porcelain  crucible)  separately  in  a  hard  glass  test-tube.    Ob- 
serve whether  any  gas  is  given  off,  and  apply  the  test  of  the 
glowing  splinter  of  wood  [See  note].     If  the  Bunsen  flame 
proves  inadequate,  try  the  blast-lamp.    Describe  the  residues. 

Notes. —  Use  the  clamp  and  ring-stand  to  support 
the  tube,  or  grasp  it  by  means  of  a  strip  of  folded  paper 
(Fig.  6).  In  either  case  it  must  be  kept  in  a  horizontal 
position,  otherwise  condensed  moisture  may  run  down 
and  cause  it  to  crack. 

Use  a  long  splinter  of  wood  [Side-shelf],  not  a  match 
(why?). 

Clean  the  test-tube  carefully  with  hot  nitric  acid 
Fig*6.     an^  dr/  it  after  each  experiment. 

Beginning  with  this  chapter  include  in  your  notes 
equations  for  all  the  chemical  changes  you  observe.  When  no 
change  is  observed,  do  not  attempt  to  give  an  equation.  In  the 
present  experiments  the  formulae  of  the  materials  used  will 
have  to  be  sought  in  the  text-book.  The  formulas  of  the  pro- 
ducts will  also  be  sought  in  the  book  after  the  appearance  of 
the  product  and  the  evolution  or  non-evolution  of  oxygen  have 
been  noted  and  an  indication  of  what  to  seek  for  has  thus  been 
obtained. 

Commercial    manga-    f  "_     -  f~J^^ 

n  e  s  e    dioxide    sometimes 
contains  charcoal,  and  it 
is  therefore  dangerous  to 
use  it  for  mixing  with  po- 
tassium chlorate  in  mak-  Fig.  7. 
ing  oxygen  in   2  without 
first  heating  a  little  alone.    Signs  of  glowing  indicate  the  pres- 
ence of  a  combustible  substance. 

2.  PREPARATION.     Mix  on  paper  about  5  g.  of  potassium 
chlorate  and  3  g.  of  powdered,  dried  manganese  dioxide. 
Put  the  mixture  in  a  hard  glass  test-tube  closed  with  a  cork 
and  fitted  with  a  delivery  tube  (Fig.  7).    Test  the  apparatus 
to  see  that  it  is  air-tight.    Clamp  the  test-tube  on  the  stand. 
Heat  carefully,  so  as  not  to  cause  too  violent  an  evolution  of 
gas,  and  collect  in  four  bottles  over  water.    Remove  the  deliv- 


12 


OXYGEN 


ery  tube  from  the  water  as  soon  as  the  bottles  are  full  (why?). 
When  the  test-tube  is  cold,  the  contents  may  be  cleaned  out 
by  allowing  them  to  soak  in  cold  water. 

3.  PROPERTIES. 

a.  Lower  a  little  ignited  sulphur  in  a  deflagrating  spoon 
into  one  bottle  (?).     Remove  the  spoon,  add  a  little  water, 
close  with  the  hand,  and  shake  ( ?).    Test  the  water  with  blue 
litmus  paper  Or  solution  [R]. 

b.  Lower  a  very  small  piece  of  burning  phosphorus  in 
the  spoon  into  the  second  bottle  in  the  same  way  ( ?).     [In- 
structions:  Phosphorus    must  always  be    cut    under   water 
and  handled  with  forceps.     Great  care  must  be  taken  not  to 
touch  it  with  the  hand,  as  it  catches  fire  easily,  and  causes 
very  severe  burns.    Red  phosphorus  is  safer,  and  should  be 
substituted  here  if  available.] 

Proceed  as  in  a  ( ?).    Test  with  blue  litmus  [R]. 

c.  Lower  a  splinter  of  glowing  charcoal  into  the  third 
bottle,  holding  it  in  the  tongs  or  wrapping  the  end  of  a  piece 
of  copper  wire  round  it  ( ?).     Treat  as  before  ( ?).     Test  with 
lime  water  [R]. 

4.  CHEMICAL  ACTIONS    INVOLVED    IN   THE   PREPARATION   OF 
OXYGEN  [Quant.,  balance]. 

a.  Devise  a  way  of  separating  the  substances  left  in  the 
tube  used  in  2  and  of  ascertaining  whether  the  manganese 
dioxide  has  been  altered.  Consult  the  instructor  in  regard  to 
the  details  of  your  plan  before  proceeding  to  execute  it. 
Weigh  tl^e  manganese  dioxide.  Do  not  use  any  delivery  tube 
or  collect  the  oxygen.  Recover  the  potassium  chloride  and 
compare  its  appearance  with  that  of  the  chlorate.  Test  solu- 
tions [Side-shelf]  of  each  with  silver  nitrate  solution  and  explain 
the  result  [R]. 

5.  SLOW  OXIDATION  OF  METALS.     Devise  a  way  of  showing 
that  air  loses  a  part  of  its  substance  when  moist  iron  filings 
rust,  and  try  it.     Submit  your  arrangement  to  the  instructor 
for  criticism. 

6.  WEIGHT    OF    A    LITER    OF    OXYGEN,    USING    ASPIRATOR 
[Quant.]. 

a.  Powder  some  potassium  chlorate,  and  dry  it  on  a  watch 
glass  on  the  radiator  or  high  above  a  small  Bunsen  flame. 
Construct  an  aspirator  (Fig.  8),  using  the  1 -liter  bottle, 
and  connect  it  with  a  hard  glass  test-tube.1  Fit  a  nozzle  to 

1  Really  infusible  test-tubes  often  cannot  be  obtained.  They 
have  to  be  made  to  order.  Test-tubes  made  by  the  students  them- 
selves from  good  combustion  tubing  are  more  trustworthy. 


OXYGEN  13 

the  rubber  tube.  Test  the  apparatus  to  see  that  all  the  joints 
are  air-tight  [Instructions  :  Place  some  water  in  the  bottle, 
blow  a  few  bubbles  of  air  into  the  apparatus  through  the 
syphon,  and  observe  whether  the  water  remains  permanently 
elevated  in  the  vertical  tube].  Fill  the  bottle  with  water  so 
that  the  short  tube  is  not  immersed.  Fill  the  rubber  tube 
and  nozzle  completely  with  water  and  close  the  clamp. 
Weigh  the  hard  glass  tube,  put  into  it  about  1  gr.  of  the  chlo- 
rate, weigh  again,  and  connect  with  the  bottle.  The  weight  of 


On  p.  13,    third    line   from   the   bottom.      Delete   the    words 
"adding  water  to  or" 


chlorate  taken,  whatever  it  may  be,  must  be  known  exactly:  it 
should  not  much  exceed  1  gr.  Allow  the  rubber  tube  to  hang 
to  the  bottom  of  a  beaker  (400  c.c.)  containing  some  water. 
Open  the  clamp  and  raise  the  beaker  till  the  levels  of  the 
water  in  this  and  the  bottle  are  the  same,  and  the  gaseous 
pressure  therefore  alike  in  both.  Close  the  clamp  again, 
empty  the  beaker,  and  replace  it. 

Open  the  clamp  once  more  and  decompose  the  salt  slowly 
by  heating,  catching  in  the  beaker  the  water  driven  over  by 
the  gas.  Stop  heating  if  the  tube  shows  signs  of  softening, 
or  when  the  decomposition  is  complete.  For  the  purpose  of 
this  experiment  (see  6,  6)  it  is  not  necessary  that  the  action 
should  be  carried  to  completion.  If,  when  the  heating  is 
stopped,  the  nozzle  is  not  under  water,  raise  the  beaker  until  it 
is  well  covered.  Allow  the  whole  apparatus  to  stand  until  it  has 
reached  the  temperature  of  the  air.  Some  water  will  return 
to  the  bottle  by  the  tube  during  the  cooling.  Admission  of 
air  to  the  tube  through  the  nozzle  at  any  stage  of  the  opera- 
tions will  prevent  this  transference,  which  is  essential  to  the 
success  of  the  experiment.  Equalize  the  level  of  the  water  in 
both  vessels  by  ftdrh'riff  wat°T  fr>  ^  raising  or  lowering  the 
beaker,  and  then  close  the  clamp. 

Measure  the  volume  of  water  in  the  beaker  by  weighing 


OXYGEN 

the  vessel  first  with  and  then  without  the  water  on  the  labo- 
ratory scales  and  subtracting.  It  will  be  equal  to  that  of  the 
gas  evolved  (what  of  the  air  originally  in  the  apparatus?). 
Weigh  the  tube  once  more  with  care,  and  observe  the  tempera- 
ture and  pressure  of  the  air. 

Subtract  the  aqueous  tension  at  the  observed  temperature 
(see  Appendix)  from  the  barometric  reading  to  get  the  true 
(partial)  pressure  of  oxygen  in  the  bottle.  Reduce  the  volume 
to  0°  and  760  mm.  Subtracting  the  weight  of  the  salt  remain- 
ing from  that  of  the  chlorate  gives  the  weight  of  this  volume 
of  oxygen.  Calculate  the  weight  of  1  liter  and  the  volume  of 
32  gr. 

Test  aqueous  solutions  of  the  chloride  and  chlorate  with 
silver  nitrate  solution  and  explain  the  result  [R]. 

To  what  class  of  gases  would  the  use  of  the  aspirator  be 
confined  for  purposes  like  the  above? 

b.  If  the  condition  of  the  hard  glass  tube  from  6,  a  will 
permit,  detach  and  heat  it  with  its  contents  once  more  to  drive 
out  the  last  traces  of  oxygen.  Allow  it  to  cool  and  weigh  it. 
Obtain  the  weights  of  chloride  and  total  oxygen  by  difference. 

Calculate  the  ratio  of  the  weight  of  the  potassium  chloride 
to  that  of  the  oxygen,  assuming  the  formula  of  the  former 
(KC1)  and  its  formula  weight  74.5  (74.5  :  x). 

Assuming  the  combining  weight  of  oxygen  to  be  16,  deter- 
mine the  formula  of  the  chlorate. 

Show  how  this  gives  the  equation  for  its  decomposition  by 
heat. 


CHAPTER  V. 

EQUIVALENT   WEIGHTS,    FORMULAE,   AND   EQUATIONS. 

1.  COMPOSITION  OF  CARBON  DIOXIDE  [Quant.]. 

Note. —  Two  students  may  with  advantage  carry  out  this 
experiment  together. 

Fit  a  piece  of  hard  glass  tubing,  25-30  cm.  long,  with  per- 
forated corks  and  insert  at  one  end  a  short  piece  of  glass 
tubing  and  at  the  other  a  U  tube,  as  in  Fig.  9.  The  inner 
edges  of  the  hard  glass  tube  should  be  rounded  with  a  file  or 
flared  by  use  of  the  blast-lamp  and  a  piece  of  charcoal. 


Fig.  9. 

Rubber  stoppers  will  give  tight  joints  more  surely  than  corks. 
Attach  to  the  U  tube  by  means  of  a  cork  a  short  straight  tube, 
of  the  diameter  of  a  narrow  test-tube,  which  has  been  drawn 
out  so  as  to  leave  a  small  opening  at  the  free  end.  Arrange  a 
loop  of  wire  with  which  to  suspend  the  potash  tubes  from  the 
balance.  Place  in  the  hard  glass  tube  a  plug  of  granular 
cupric  oxide,  or  an  oxidized  roll  of  copper  gauze,  about  4  cm. 
in  length.  The  former  may  be  held  in  position  by  small 
wads  of  asbestos.  The  cupric  oxide  and  asbestos  must  be 
dried  by  heating  in  the  porcelain  crucible  before  use.  Put 
about  0.2  g.  of  pure  dry  sugar-charcoal  [Storeroom]  in  a 
porcelain  boat,  weigh  the  boat  with  contents,  and  set  it  in  the 
tube  close  behind  the  cupric  oxide.  Make  a  few  c.c.  of  a 
strong  (approximately  30  per  cent.)  solution  of  potassium 
hydroxide,  fill  the  bend  of  the  U  tube  with  it,  and  charge  the 
small  tube  beyond  with  fragments  of  solid  caustic  potash. 
Test  the  apparatus  to  see  that  it  is  air-tight  [Instructions]. 
Finally,  weigh  the  connected  potash  tubes  immediately  before 
starting  the  combustion,  suspending  them  on  the  balance  by 
means  of  a  thread. 

Slip  the  cylinder  of  wire  gauze  over  the  hard  glass  tube, 
connect  the  latter  with  the  oxygen  cylinder  (or  other  source 


16        EQUIVALENT    WEIGHTS,    FORMULAE,    EQUATIONS 

of  oxygen),  and  heat  the  part  containing  the  boat  and  cupric 
oxide  with  two  burners  [Temp,  order].  Turn  on  the  oxygen 
with  care  and  regulate  the  stream  so  that  the  carbon  may 
burn  slowly  and  not  more  than  15-20  bubbles  of  unused 
oxygen  escape  per  minute.  A  more  rapid  stream  will  involve 
the  loss  of  carbon  dioxide.  Heat  the  front  of  the  boat  first 
and  let  the  glow,  caused  by  the  combustion,  travel  along. 
The  burning  will  take  30-45  minutes.  Continue  the  stream 
of  oxygen  for  4-5  minutes  after  the  carbon  is  completely 
burned  (why?),  then  disconnect  the  potash  apparatus  and 
weigh  it.  A  more  accurate  result  is  obtained  by  finally  dis- 
placing the  oxygen  by  air  (why?).  After  the  tube  has  cooled, 
weigh  the  boat  with  any  ash  it  may  contain.  Return  the 
cupric  oxide  to  the  bottle. 

The  loss  in  weight  of  the  boat  gives  the  amount  of  carbon; 
the  gain  in  weight  of  the  potash  apparatus,  the  amount  of 
carbon  dioxide.  The  difference  of  these  two  gives  the  oxygen. 

Calculate  the  percentage  composition  of  carbon  dioxide 
and  the  weight  of  carbon  combining  with  8  parts  of  oxygen. 
This  gives  the  equivalent  weight  of  carbon. 

Assuming  the  atomic  weights  of  carbon  and  oxygen  to  be 
12  and  16  respectively,  calculate  the  formula  of  carbon  dioxide 
from  the  percentage  composition. 

Make  the  equation  representing  the  action. 

What  would  be  the  formula  of  the  compound  if  the  sym- 
bols represented  the  equivalent  weights? 

2.  COMPOSITION  OF  AN  OXIDE  OF  A  METAL  [Quant.]. 

On  account  of  the  difficulties  attending  the  making,  the 
collecting,  or  t^e  weighing  of  most  oxides  formed  by  direct 
union,  the  following  indirect  method  is  suggested.  It  consists 
in  converting  a  known  weight  of  a  metal  into  nitrate  by  the 
action  of  nitric  acid  and  obtaining  the  oxide  by  ignition  of  this 
salt  (attempt  no  equations  for  these  actions). 

a.  Weigh  an  evaporating-dish  of  medium  size,  place  in  it 
about  0.5  g.  (6  inches)  of  pure  iron  wire  [Storeroom],  and 
weigh  again.  Cover  the  dish  with  a  watch  glass,  convex  side 
downward,  and  add  5  c.c.  of  pure  dilute  nitric  acid.  Set  the 
dish,  covered,  on  the  steam  bath  until  the  iron  has  dissolved. 
Then  rinse  the  cover-glass  carefully  into  the  dish  and  evapo- 
rate the  solution  to  dryness  on  the  steam  bath  or  on  a  beaker 
of  boiling  water  [Hood].  When  residue  (what  is  it  ?)  is  dry, 

Elace  the  dish  on  a  wire  gauze  and  heat  carefully  with  a 
urner  held  in  the  hand  as  long  as  any  red  fumes  are  given 
off.     Allow  the  dish  and  contents  (?)  to  cool  and  weigh  them. 
To  make  sure  that  the  decomposition  was  complete,  heat  once 


EQUIVALENT    WEIGHTS,   FORMULA,    EQUATIONS        17 

more,  cool,  and  weigh  again.  This  precaution  is  always 
necessary  in  experiments  of  this  nature. 

Assuming  the  equivalent  weight  of  oxygen  as  8,  calculate 
that  of  the  iron  in  the  oxide. 

Assuming  the  combining  weights  of  iron  and  oxygen  to 
be  56  and  16  respectively,  determine  the  formula  of  the  com- 
pound. 

6.  Pure  zinc  (about  0.5  g.)  may  be  used  instead  of  iron. 
The  manipulation  is  the  same  as  in  2,  a.  The  residue  from 
evaporation  is  a  syrup-like  body,  however,  which  cannot  be 
dried.  Extra  caution  must  be  used  in  heating  this  to  avoid 
loss  by  spirting. 

Answer  the  same  questions  as  in  2,  a. 

3.  EQUIVALENT  WEIGHT  OF  A  METAL  BY  DISPLACING  HYDROGEN 
[Quant.]. 

a.  First  fill  the  pneumatic  trough  and  1-liter  bottle  with 
water  so  that  the  latter  may  acquire  the  temperature  of  the 
room.  Boil  about  half  a  liter  of  water  and  allow  it  to  cool. 
Fit  a  100  c.c.  flask  somewhat  as  in  Fig.  10,  using  in  place  of 
the  thistle-tube  a  dropping-f  unnel.  To  carry  a  doubly  bored 
cork  the  mouth  of  the  flask  must  be  rather  wide.  A  larger 
flask  than  100  c.c.  must  not  be  used  on  account  of  the  waste 
of  acid  it  would  entail.  The  stem  of  the  dropping-funnel 
must  reach  to  the  bottom  of  the  flask,  and  the  inner  end  of 
the  other  tube  must  be  flush  with  the  bottom  of  the  cork. 
Attach  a  rubber  or  glass  delivery  tube  and  see  that  the  appa- 
ratus is  air-tight.  Weigh  a  piece  of  chemically  pure  zinc, 
taking  about  2  g.  Without  detaching  your  platinum  wire 
from  the  glass  rod,  wrap  it  tightly  round  the  zinc  (why?)  and 
allow  the  whole  to  slide  gently  into  the  flask.  Fill  the  appa- 
ratus completely,  from  the  top  of  the  stem  of  the  funnel  to 
the  tip  of  the  delivery  tube,  with  part  of  the  boiled  water. 
Close  the  stop-cock  when  the  bulb  has  almost  emptied  itself. 
Invert  the  1-liter  bottle,  filled  with  water,  on  the  shelf  of  the 
pneumatic  trough,  and  put  the  delivery  tube  in  position. 

Half  fill  the  globe  of  the  funnel  with  pure  concentrated 
hydrochloric  acid  [Side-shelf]  and  admit  this  to  the  flask,  a 
little  at  a  time,  in  such  a  way  that  a  steady,  but  not  too  violent, 
action  takes  place.  When  the  metal  is  entirely  dissolved, 
drive  all  the  gas  over  into  the  bottle  by  pouring  boiled  water 
once  more  through  the  funnel  (be  careful  that  no  air  is  carried 
with  the  water). 

When  the  gas  has  acquired  the  temperature  of  the  water 
and  room,  lower  the  bottle  until  the  level  of  the  water  outside 
and  inside  is  the  same.  Close  the  bottle  while  it  is  in  this 


18        EQUIVALENT    WEIGHTS,    FORMULA,    EQUATIONS 

position  with  a  cork  and  remove  it  from  the  trough.  Weigh 
the  bottle  as  it  stands  on  the  laboratory  scales,  and  also  com- 
pletely filled  with  water,  and  subtract,  to  find  the  volume  of 
the  gas.  Take  the  -temperature  and  barometric  pressure. 
Subtract  from  the  latter  the  aqueous  tension  (Appendix). 
Find  by  calculation  (1  liter  weighs  .09  g.  at  0°  and  760  mm.) 
the  weight  of  the  hydrogen  obtained.  Calculate  the  equiva- 
lent weight  of  zinc,  i.  e.,  the  weight  of  the  metal  which  dis- 
places 1.0076  g.  of  hydrogen.  Wash  the  trough  carefully 
until  it  is  absolutely  free  from  acid  and  put  it  away  in  an 
inverted  position  to  avoid  rusting. 

b.  The  experiment  may  be  performed  with  magnesium 
(about  0.7  g.— 65  cm.  of  No.  23  wire),  iron  (about  1.5  g.), 
or  aluminium  (about  0.8  g.)  in  place  of  zinc. 

In  the  absence  of  a  dropping-f  unnel,  a  substitute  may  be 
made  by  connecting  a  funnel  with  a  straight  tube  by  means 
of  a  rubber  joint  closed  with  a  pinch  clamp.  Or,  the  aspirator 
(Fig.  8)  may  be  used  here,  the  metal  (half  the  above  quantities), 
water,  and  a  smaller  tube  containing  the  acid  being  placed  in 
a  test-tube,  and  the  mixing  being  effected  by  inclining  the 
bottle  after  the  apparatus  is  connected. 

4.  INTER-EQUIVALENCE   OF  EQUIVALENT    WEIGHTS    [Law  of 
Reciprocal  Proportions]. 

If  2,  b  was  performed,  compare  the  quantity  of  zinc  which 
combined  with  8  g.  of  oxygen  with  that  which  in  3,  a  was 
found  to  displace  1.0076  g.  of  hydrogen.  If  they  are  iden- 
tical, these  two  quantities  of  oxygen  and  hydrogen  may  com- 
bine with  one  another.  What  substance  has  precisely  this 
composition  ? 

5.  COMPOSITION   OF  ZINC  CHLORIDE  [Quant.].    (From  Tor- 
rey's  Elementary  Studies.) 

Weigh  an  evaporating-dish  of  medium  size  and  place  in 
it  about  2  g.  of  pure  zinc.  Add  a  little  diluted  (1:2),  pure, 
concentrated  hydrochloric  acid  [Side-shelf]  and  cover  with  a 
watch  glass,  convex  side  downward.  If  the  action  is  very 
slow,  the  tip  of  a  platinum  wire  may  be  placed  in  contact 
with  the  zinc.  Maintain  a  brisk  action  by  further  additions 
of  concentrated  hydrochloric  acid  in  very  small  amounts 
at  a  time.  Final  excess  of  the  acid  should  be  avoided,  as 
time  will  be  lost  in  the  subsequent  evaporation.  When  the 
metal  is  completely  dissolved,  rinse  the  cover-glass  and  pla- 
tinum wire  carefully  into  the  porcelain  dish  and  remove  them. 
Allow  the  solution  to  evaporate  as  far  as  possible  on  the  steam 


EQUIVALENT    WEIGHTS,    FORMULAE,    EQUATIONS        19 

bath  or  on  a  beaker  of  boiling  water  [Hood].  Now  place  the 
dish  on  the  ring-stand  and,  using  a  small  Bunsen  flame,  allow 
the  syrup-like  solution  to  evaporate  slowly  to  dryness.  Then 
heat  the  white  mass  to  the  point  at  which  it  has  completely 
melted  and  no  further.  The  best  way  to  achieve  this  with  the 
minimum  rise  in  temperature  is  to  let  the  Bunsen  flame  play 
on  the  surface  from  above.  Overheating  must  be  avoided, 
because  the  product  is  volatile  at  high  temperatures.  The 
moment  the  dish  has  so  far  cooled  that  the  hand  can  be  borne 
upon  the  bottom,  wipe  the  dish  carefully  and  weigh  it.  The 
substance  absorbs  moisture  greedily  from  the  atmosphere, 
hence  expedition  is  required  in  cooling  and  weighing  if  accu- 
rate results  are  to  be  obtained.  To  insure  accuracy,  the  melt- 
ing, cooling,  and  weighing  should  be  repeated,  and  the  lower 
result  taken  as  correct. 

Using  the  equivalent  weight  of  zinc  obtained  in  3,  a,  cal- 
culate the  equivalent  weight  of  chlorine. 

Assuming  the  combining  weights  of  zinc  and  chlorine  to 
be  65  and  35.5  respectively,  determine  the  formula  of  zinc 
chloride. 

Using  the  result  of  3,  a,  find  how  many  combining  weights 
of  hydrogen  are  displaced  by  65  parts,  the  combining  weight, 
of  zinc.  What  is  the  valence  of  zinc? 

Express  the  whole  action  of  hydrochloric  acid  on  zinc  in 
symbols  by  making  the  equation  in  accordance  with  these 
conclusions. 

6,  MULTIPLE  PROPORTIONS  [Quant.]. 

a.  [Two  students  working  together.]  Fit  a  hard  glass  tube, 
25-30  cm.  long,  with  corks,  through  which  pass  short  pieces 
of  narrow  glass  tubing.  To  one  of  these  connect  a  Kipp's 
apparatus  for  generating  hydrogen  and  a  gas  washing  bottle 
(shown  in  Fig.  12)  one-half  full  of  concentrated  sulphuric 
acid.  Make  sure  that  the  apparatus  is  air-tight.  Dry  some 
powdered  cupric  oxide  by  heating  it  in  a  hard  glass  test-tube. 
Weigh  two  clean,  dry,  porcelain  boats  [Temp,  order]  and  place 
in  one  about  1  g.  of  the  cupric  oxide  and  weigh  again.  Have 
about  1  g.  of  pure  cuprous  oxide  [Storeroom1]  placed  in 
the  other  and  weigh  likewise.  Be  careful  in  recording  the 
weights  and  in  handling  the  boats  to  distinguish  the  one 
from  the  other.  Place  the  boats  in  the  hard  glass  tube,  that 
containing  cupric  oxide  in  front,  and  surround  it  with  a  piece 
of  wire  gauze. 

'Pure  cuprous  oxide  (Kahlbaum's)  can  be  kept  successfully 
if  sealed  up  in  small  bottles  which  are  not  opened  until  needed. 


20        EQUIVALENT    WEIGHTS,    FORMULA,    EQUATIONS 

Pass  a  gentle  stream  of  gas  through  the  apparatus  until  a 
test  ( ?)  shows  that  the  air  has  all  been  displaced.  Now  heat 
the  boats  moderately,  beginning  with  the  front  one.  What 
collects  in  the  rear  of  the  boat?  Where  does  it  come  from? 
When  the  action,  which  requires  10-15  minutes,  is  finished, 
allow  the  boats  to  cool  in  a  stream  of  hydrogen.  Weigh  the 
boats  and  contents  (?),  taking  care  not  to  interchange  them. 
To  ascertain  whether  the  action  is  complete  heat  the  boats 
once  more  in  hydrogen,  cool,  and  weigh  again. 

Assuming  the  equivalent  weight  of  oxygen  to  be  8,  calcu- 
late, from  your  results,  that  of  copper  in  each  oxide.  What 
is  the  ratio  of  the  two  values  for  copper? 

Using  your  results,  and  assuming  16  and  63.6  to  be  the 
atomic  weights  of  oxygen  and  copper  respectively,  find  the 
formula  of  each  oxide.  Construct  the  equations  represent- 
ing the  action  of  hydrogen. 

b.  If  the  experiment  in  Chap.  IV,  6,  6,  (p.  14)  was  carried 
out,  dried  potassium  perchlorate  may  de  decomposed  in  the 
same  way  and  the  results  compared.     Simply  use  an  open, 
long,  hard  glass  test-tube,  without  aspirator,  and  drive  off  the 
oxygen  slowly. 

Calculate  the  ratio  of  the  weight  of  the  potassium  chlo- 
ride (KC1)  to  that  of  the  oxygen,  assuming  the  formula  weight 
of  the  former,  74.5,  as  before  (74.5  :x').  Compare  the  value 
of  x'  with  that  of  x  in  the  former  experiment.  What  are  the 
smallest  integers  which  will  express  their  ratio  (x :  x ' )  ? 

Assuming  the  atomic  weight  of  oxygen  to  be  16,  deter- 
mine from  your  results  the  formula  of  the  perchlorate. 

Construct  the  equation  for  the  action. 

c.  Pure  lead  dioxide  and  pure  lead  monoxide  may  be  used 
as  in  a,  if  available.     The  monoxide,  however,  absorbs  carbon 
dioxide  readily  from   the  air,  and  therefore  does   not  keep 
well.     It  is  also  more  difficult  to  reduce  than  the  dioxide. 
The  heating  in  a  stream  of  hydrogen  must  be  repeated  to 
constant  weight. 

7.  DULONG  AND  PETIT'S  LAW.  The  specific  heats  of  the 
metals  used  in  this  chapter  are: 

Aluminium  0.214  Lead  0.031 

Copper          0.095  Magnesium  0.250 

Iron  0.114  Zinc  0.095 

According  to  Dulong  and  Petit,  if  the  correct  atomic 
weight,  when  it  has  been  found,  is  multiplied  by  the  specific 
heat  of  the  element  in  the  solid  form,  the  product  is  a  number 
which  in  most  cases  lies  between  6  and  6.8. 


EQUIVALENT   WEIGHTS,   FORMULA,    EQUATIONS        21 

Take  the  values  of  such  combining  weights  and  equiva- 
lents as  you  have  found  experimentally  in  2  (iron  or  zinc),  3 
(zinc,  magnesium,  iron,  or  aluminium),  5  (zinc),  6  (copper),  and 
multiply  each  by  the  corresponding  specific  heat.  If  the  re- 
sult is  about  6.4,  the  atomic  weight  is  the  same  as  the  equiva- 
lent weight.  If  not,  multiply  the  equivalent  weight  by  the 
smallest  integer  which  will  bring  the  final  product  within  the 
limits  6  to  6.8.  The  integer  used  is  the  valence  of  the  ele- 
ment, and  the  product  of  equivalent  weight  into  the  valence  is 
the  atomic  weight. 


CHAPTER  VI. 

HXDROGEN. 

1.  INTERACTION  OF  METALS  AND  ACIDS. 

a.  Place  a  small  piece  of  each  of  the  metals,  tin  (gran.), 
copper  (turnings),  iron  (filings),  zinc  (gran.,  large  bottle),  lead 
(gran.),  aluminium  (wire),  and  magnesium  (wire)  in  separate 
test-tubes  and  add  to  each  a  little  pure  [Side-shelf]  concen- 
trated hydrochloric  acid.    (What  is  the  nature  of  this  liquid? 
[R.])    Observe  each  case  critically,  and  record  the  results, 
noting  the  order  of  the  metals  in  respect  to  activity.    Note  the 
effect  of  heating,  if  no  action  occurs  in  the  cold.     If  heating 
seems  to  produce  gas,  remember  that  it  may  be  hydrogen 
chloride  or  steam  and  not  hydrogen.     It  will  be  necessary  to 
use  discrimination  in  deciding  this  point.     After  the  action 
has  ceased,  filter  any  one  of  the   solutions   and  evaporate 
[Hood]  it  to  dryness  on  the  sand  bath  ( ?). 

Can  you  give  any  grounds  for  the  belief  that  the  hydrogen 
comes  from  the  acid  and  not  from  the  metal  or  the  water? 

b.  Ascertain  the  influence  of  the  physical  state  of  the  metal 
on  its  apparent  activity  by  using  zinc  dust  with  the  same  acid. 

c.  Try  in  the  same  way  the  action  of  dilute  sulphuric  acid 
on  copper,  zinc  (pure),  and  iron.     In  case  little  or  no  action 
takes  place  in  the  cold,  try  the  effect  of  putting  a  platinum 
wire  in  contact  with  the  metal  ( ?)  and,  having  withdrawn  the 
wire,  of  adding  a  drop  of  cupric  sulphate  solution  to  the  two 
last  ( ?)  before  resorting  to  heating.     If  any  effect  is  observed, 
notice  where  the  hydrogen  appears  to  come  from,  and  explain 
[R].     When  the  acid  has  been  exhausted  by  the  action  of  the 
last  metal  (of  which  excess  must  be  used)  filter  the  solution 
while  it  is  still  warm  from  the  action,  and  set  it  aside  on  the 
shelf  of  your  cupboard  to  crystallize  [Instructions  and  notes 
below]. 

d.  Try  the  action  of  strong  acetic  acid  on  iron 

e.  For  comparison,  study  the  action  of  a  little  concen- 
trated sulphuric  acid  on  zinc  (gran.)  in  the  cold  and  in  the 
heat.     What  products  are  formed? 

Notes. —  In  observing  an  interaction  a  chemist  first  mixes  the 
substances  thoroughly  by  shaking.  If  nothing  occurs,  he  then 
heats.  If  his  eye  shows  evidence  of  the  production  of  a  gas  or 
vapor,  he  finally  smells  the  contents  of  the  tube.  Apply  these 

22 


HYDROGEN  23 

three  methods  of  observation  to  e  before  drawing  any  conclusion. 
In  making  the  equations  for  the  above  actions  all  that  is 
needed,  beyond  the  information  given  above  and  acquired  by 
observation,  is  to  find  the  formulas  of  the  products.  These  are 
not  here  to  be  sought  by  measurement,  but  in  the  text-book  [R]. 

2.  INTERACTION  OF  METALS  AND  WATER. 

a.  Recall  the  action  of  sodium  and  potassium  on  water 
[Lecture]. 

6.  [Two  students  working  together.]  Place  about  20  cm. 
of  magnesium  ribbon,  twisted  into  a  knot,  in  the  higher  end 
of  an  inclined  hard  glass  delivery  tube.  Fit  a  250  c.c.  flask, 
like  that  used  in  generating  hydrogen  (Fig.  10),  and  heat  some 
water  in  it  until  a  regular  stream  of  steam  issues.  If  the 
stream  is  unsteady,  put  some  broken  porcelain  into  the  flask. 
Now  heat  the  magnesium  with  another  burner,  connect  the 
flask  so  as  to  pass  steam  over  the  heated  metal,  and  collect 
the  resulting  gas  over  water  in  a  bottle.  When  enough  has 
been  collected,  or  the  magnesium  is  all  oxidized,  remove  the 
delivery  tube  from  the  water,  and  apply  a  light  to  the  gas  in 
the  bottle. 

c.  The  molecule  of  sodium  hydroxide,  formed  from  a  mole- 
cule of  water  in  a,  may  undergo  further  change  by  heating 
with  a  fresh  quantity  of  sodium.     It  is  more  convenient  to 
use  another  metal  for  the  purpose,  however. 

Prepare  a  hard  glass  test -tube  and  a  delivery  tube.  Rap- 
idly powder  some  sodium  hydroxide  (1  part),  mix  it  with  zinc- 
dust  (Imparts),  heat  in  the  tube  clamped  in  a  horizontal  position, 
and  collect  the  gas  over  water.  Ascertain  whether  the  gas  is 
combustible.  What  information  about  the  original  molecule 
of  water  do  the  results  of  a  and  c  together  give  us  ?  What  is 
the  solid  product  in  c  [R]? 

d.  Place  about  5  g.  of  granulated  zinc  in  a  test-tube  and 
let  it  stand,  for  a  few  seconds  only,  with  a  dilute  solution  of 
cupric  sulphate  ( ?).   Pour  off  the  solution  and  add  some  water. 
Take  special  care  not  to  shake  with  air,  as  the  copper  is  easily 
oxidized  and  its  effect  impaired.     Fit  the  test-tube  with  a 
cork  and  delivery  tube  and  boil  persistently,  using  a  small 
flame.   After  the  air  in  the  tube  has  been  completely  displaced 
by  steam,  collect  the  gas,  which  comes  off  very  slowly,  over 
water  in  a  test-tube.     Determine  whether  it  is  combustible. 
Make  a  general  statement  about  zinc  on  the  basis  of  1,  a  and 
c,  and  2,  d ;  also  about  the  hydrogen  in  water  and  acids. 

3.  PREPARATION  OF   HYDROGEN   [Same   apparatus   is  used 
for  4  and  5]. 

a.  Put  some  granulated  zinc  [Large  bottle]  in  a  250  c.c. 


24  HYDEOGEN 

flask  (Fig.  10)  provided  with  a  rubber  delivery  tube,  add  diluted 
hydrochloric  acid,  and  test  the  issuing  gas  till  it  is  found  free 
from  air.  [Instructions :  The  gas  must  not  be  ignited  at  once, 
or  the  apparatus  may  be  blown  up.  Samples  must  be  caught 
in  test-tubes,  held  bottom  up,  and  the  tubes  must  be  brought 
to  a  distant  flame  in  the  same  position. 
If  the  gas  contained  in  them,  after  the  first 
explosion  of  the  part  nearest  to  the  mouth, 
burns  quietly,  the  gas  is  free  from  air.] 

Ascertain  whether  ordinary  combusti- 
bles burn  in  the  gas.  Show  whether  it  is 
lighter  or  heavier  than  air.  Fill  a  test- 
tube  with  one-third  hydrogen  and  two- 
thirds  air  and  apply  a  light  to  the  mixture. 
Keep  the  apparatus  in  operation  for  use 
in  4  and  5. 

Fig.  10.  T-» 

4.  PRODUCT  OF  THE  UNION  OF  HYDRO- 
GEN AND  OXYGEN.  Attach  a  glass  tube,  drawn  out  to  a  capil- 
lary opening,  in  place  of  the  delivery  tube.  Ascertain  that 
the  issuing  gas  is  not  explosive  (test?).  Hold  a  cold,  dry 
beaker  close  against  the  jet  of  unlighted  gas  (?).  If  moisture 
is  deposited  (what  is  its  source?),  insert  a  U  tube  filled  with 
chloride  of  calcium  to  dry  the  gas.  When  the  gas  no  longer 
deposits  moisture,  set  fire  to  it  and  hold  the  beaker  over  the 
flame  (?). 

Burn  ordinary  illuminating  gas  from  the  same  nozzle  and 
hold  the  beaker  over  the  flame  (?). 

5.  REDUCTION. 

a.  [Two  students  working  together.]  Fit  a  hard  glass 
tube  open  at  both  ends  with  perforated  corks  and  short  tubes. 
Place  aluminium  oxide,  ferric  oxide,  and  minium,  one  at  a 
time,  in  the  tube  near  the  end  next  to  the  generator,  but  not 
so  near  as  to  endanger  the  corks  when  heat  is  applied.  Dry 
each  oxide  by  heating  in  a  porcelain  crucible  before  use. 
Support  the  tube  on  the  stand  by  means  of  a  clamp  attached 
close  to  one  end,  connect  it  with  an  apparatus  delivering  dry 
(see  4)  hydrogen.  [Use  the  generator  made  in  3,  or  a  Kipp's 
apparatus,  as  a  source  of  hydrogen.]  Heat  each  oxide  in  a 
slow  stream  of  the  gas.  After  each  time  the  apparatus  has 
been  opened,  wait  till  the  air  has  been  displaced  by  hydrogen 
before  heating  (why?  test?).  Observe  the  effect  on  each  oxide 
and  whether  water  condenses  in  the  tube.  If  no  effect  is  no- 
ticed after  the  oxide  has  been  at  a  red  heat  for  three  minutes, 
absence  of  action  may  be  inferred. 

Ascertain  the  common  names  of  the  oxides  used  [K].    Of 


HYDROGEN  25 

what  chemical  change  shown  in  the  lecture-room  is  the  action 
on  ferric  oxide  essentially  a  reversal?  [Advanced  students. 
What  conditions  permit  the  completion  of  the  action  in  either 
direction?  R.] 

b.  Mix  thoroughly  in  a  mortar  equal  bulks  of  magnesium 
powder  and  powdered  calcium  carbonate.  Put  the  mixture  in 
a  test-tube  (it  should  fill  about  half  an  inch  of  the  tube),  fix 
the  tube  in  a  clamp  on  the  stand,  and  heat  the  top  layer  in 
the  Bunsen  flame  until  the  reaction  begins.  It  will  go  on  to 
completion  by  itself.  Be  careful  to  keep  the  tube  directed 
away  from  the  face  during  the  heating.  Allow  the  test-tube 
to  cool,  add  a  little  water,  and  then,  slowly,  an  excess  of  con- 
centrated hydrochloric  acid  ( ?).  If  the  tube  has  been  broken, 
place  the  contents  with  the  acid  in  a  beaker.  The  acid  will 
dissolve  any  excess  of  calcium  carbonate  or  magnesium  with 
effervescence.  It  will  also  dissolve  the  oxides  of  magnesium 
and  calcium  formed  by  the  action.  The  black  material  alone 
should  remain  undissolved.  When  all  action  has  ceased,  filter 
and  wash  the  black  residue  ( ?)  with  water.  After  drying  this 
on  the  radiator  or  steam  bath,  prove  that  it  is  carbon.  This 
may  be  done  by  placing  some  of  it  in  a  dry  test-tube,  adding 
a  pinch  of  potassium  chlorate,  heating  in  the  Bunsen  flame,  and 
pouring  the  gas  when  it  has  cooled  (close  the  tube  with  the 
thumb  while  waiting  for  this)  into  a  test-tube  containing  lime 
water  and  shaking  ( ?). 

What  is  the  reducing  agent  in  this  action? 


CHAPTER  VII. 

WATER   AND  SOLUTION. 

1.  PURITY  OF  WATER.    Place  a  few  drops  of  distilled  water 
on  a  clean  watch  glass  (why  not  an  evaporating-dish?)  and 
evaporate  on  the  steam  bath.     Do  the  same  with  ordinary 
water.    Observe  whether  any  stain  remains  on   the  glass. 
What  class  of  impurities  would  leave  no  trace  of  their  presence 
in  this  test  ? 

2.  UNION  WITH  OXIDES.     Place  a  pinch  of  cupric  oxide  in  a 
test-tube  and  wash  it  by  shaking  with  a  little  distilled  water 
and  pouring  off  the  liquid.    Add  more  water  and  shake  again. 
Test  this  solution  with  neutral  litmus  paper  (?).     At  the  same 
time  test  a  sample  of  the  water  with  the  same  paper  and  com- 
pare the  tints.     Repeat  with  barium  oxide  ( ?). 

The  behavior  of  acid-forming  oxides  has  been  examined  in 
Chap.  IV,  3  (p.  12).    Recall  the  three  cases. 

3.  HYDRATES. 

a.  Heat  some  blue  vitriol  gently  in  a  porcelain  crucible  ( ?). 
Dissolve  the  white  powder  by  boiling  with   the   minimum 
amount  of  water  required  to  dissolve  it  and  set  the  solution 
aside  (?).   What  chemical  action  has  taken  place  in  each  case? 

b.  [Quant.]   Place  small  quantities  (about  1  g.)  of  Glau- 
ber's salt  and  blue  vitriol  in  two  porcelain  dishes  and  ascer- 
tain the  gross  weight  in  each  case.    Allow  the  dishes  and 
contents  to  remain  for  24  hours  or  more  and  weigh  again 
(?)  [R]. 

c.  Gently  warm  small  quantities  of  barium  chloride,  po- 
tassium nitrate,  magnesium  sulphate,  alum,  and  potassium 
dichromate  separately  in  dry  test-tubes  and  notice  whether 
they  undergo  any  change  [R]. 

Are  all  crystalline  substances  hydrates  ?  Classify  the  sub- 
stances you  have  examined  into  two  groups  with  reference  to 
this  property. 

d.  [Quant.]  Weigh  out  about  2  g.  of  crystals  of  gypsum 
in  a  porcelain  crucible.    Heat  to  redness  until  no  further  loss 
in  weight  occurs,  and  weigh  the  calcium  sulphate  remaining. 
Assuming  the  atomic  weights  of  the  elements  and  the  for- 
mulae of  the  sulphate  and  of  water,  calculate  the  formula  of 
gypsum. 


WATER    AND   SOLUTION 


27 


Fig.  11. 


4.  DELIQUESCENCE.     Set  some  potassium  carbonate  aside 
in  a  small  beaker  and  examine  it  from  day  to  day. 

5.  SOLUTION:  GASES  IN  LIQUIDS. 

a.  Half  fill  a  1 -liter  bottle  with  distilled  water,  cork,  and 
shake  vigorously  till  the  water  is  saturated  with  air.    Take 
the  temperature  of  the  water  and  the  height  of  the  barometer. 

Measure  the  content  of  a  flask 
holding  about  100  c.c.  and  fit  it 
with  a  cork  and  delivery  tube 
(Fig.  11.)  Fill  the  whole  ap- 
paratus, including  the  tube, 
completely  with  the  prepared 
water,  and  boil,  collecting  the 
gas  in  an  inverted  test-tube. 
When  no  more  comes  over,  equalize  the  levels  and  mark  the 
level  in  the  tube  with  a  thin  rubber  ring.  [Cut  this  from  your 
rubber  tubing.]  Measure  the  volume  which  the  air  occupied 
and  calculate  the  volume  of  air  dissolved  by  100  c.c.  of  water 
at  the  observed  temperature  and  pressure,  correcting  for  the 
aqueous  vapor  present  (?). 

What  proportion  of  its  own  volume  of  air  has  the  water 
dissolved? 

Note.  An  inverted  burette  partially  filled  with  water  and 
closed  at  the  top  may  be  used  in  place  of  the  test-tube,  if  proper 
correction  for  difference  in  level  of  the  water  is  made.  Divide 
the  height  of  the  water  by  13.6  to  get  the  equivalent  in  mercury 
and  subtract  from  the  barometer. 

b.  [Quant.]  Fit  up  a  gas  washing  bottle  and  test-tube 
(Fig.  12),  making  a  slight  notch  down  the  side  of  the  cork  in 
the  latter  to  permit  the  escape  of  gas.    Provide  a  short  piece 
of  wire  for  hanging  the  test- 
tube  on   the  balance.      Fill 

the   bottle  one-third  full  of 
water  (use  of  this?). 

Weigh  the  test-tube  and 
fittings,  place  in  it  about  5  c.c. 
of  water,  weigh  again,  and 
finally  support  it  in  a  beaker 
full  of  cold  water.  Connect 
a  bottle  of  liquid  sulphur  di- 
oxide [Hood]  with  the  wash- 


Fig.  12. 


ing  bottle  and  turn  on  a  slow  stream  of  the  gas.  When  the 
water  seems  to  be  saturated,  stop  the  gas.  Disconnect,  dry, 
and  weigh  the  test-tube  once  more.  Repeat  the  operation  for 
a  minute  or  so  and  weigh  again.  If  there  is  an  increase, 


28  WATER   AND    SOLUTION 

repeat  until  the  weight  is  constant.  Take  the  temperature  (£) 
of  the  water  in  the  beaker  and  the  height  of  the  barometer  (p). 
Calculate  the  weight  of  sulphur  dioxide  dissolved  by  100  c.c. 
of  water  at  the  observed  t  and  p.  Calculate  the  volume  which 
this  weight  of  gas  would  occupy  at  t  and  p.  How  many 
times  its  own  volume  of  the  gas  has  the  water  dissolved? 

State  the  law  (Henry's)  in  accordance  with  which   the 
amount  of  the  gas  dissolved  varies  with  the  pressure  [R], 

6.  SOLUTION:  LIQUIDS  IN  LIQUIDS. 

a.  Take  5  c.c.  of  alcohol  in  one  test-tube  and  an  equal 
volume  of  water  in  another.     Add  the  alcohol  to  the  water  a 
drop  or  two  at  a  time,  shake  after  each  addition,  and  observe 
whether  solution  takes  place  (?).    Repeat,  adding  water  to 
alcohol  (?). 

b.  Repeat  a  with  ether  and  water  and  with  carbon  disul- 
phide  and  water  (?),  taking  care  to  use  dry  test-tubes. 

7,  SOLUTION:  SOLIDS  IN  LIQUIDS. 

a.  Prepare  a  saturated  solution  of  potassium  dichromate 
by  pulverizing  the  salt  (about  7  g.),  placing  it  in  a  flask  con- 
taining 50  c.c.  of  water,  and  shaking  it  at  intervals  for  ten 
minutes. 

Take  the  temperature  of  the  solution.     Weigh  [Quant.] 
into  an  evaporating-dish  about  25  g.  of  the  solution.     Evap- 
orate to  dry  ness  on  the  water  bath  and  weigh  again.     Calcu- 
Jate  the  weight  of  dichromate  dissolved  by  1  liter  of  distilled 
water  at  the  temperature  observed. 

b.  Take  6  g.  of  the  dichromate  and  boil  with  10  c.c.  of 
water  in  a  test-tube.     Is  the  solubility  different?     Allow  the 
clear  solution  to  cool  (?).    Explain  the  result. 

c.  Take  5  c.c,  of  water  in  each  of  two  test-tubes.     Shake 
one  with  crystallized,  hydrated,  sodium  sulphate  (previously 
powdered  in  a  mortar)  until  no  more  dissolves.     Simulta- 
neously shake  the  other  with  powdered,  anhydrous,  sodium 
sulphate  (freshly  made  by  heating  the  hydrated   salt  in  a 
small  evaporating  dish)  until  equilibrium  is  reached.     In  the 
intervals  of  shaking  place  both  test-tubes  in  a  beaker  of  water 
until  their  temperatures  are  equal.     Ascertain  the  solubility 
of  each  kind  of  sodium  sulphate  as  in  a.     Interpret  the 
result  [R]. 

d.  Shake  some  calcium  sulphate  with  recently  boiled  dis- 
tilled water.     Ascertain  whether  any  of  the  salt   has  gone 
into  solution  or  not.     Repeat  with  chalk  (calcium  carbonate), 
rejecting  the  water  with  which  it  is  first  shaken  ( ?). 


WATER   AND    SOLUTION  29 

e.  Two  immiscible  solvents.  Place  one  small  particle  of 
iodine  in  each  of  three  test-tubes  and  add  to  one  water,  to  the 
second  potassium  iodide  solution,  to  the  third  ether,  and  shake 
each  ( ?).  If  in  any  of  the  tubes  iodine  remains  undissolved, 
pour  off  that  solution  into  a  clean  test-tube.  Now  add  a 
little  ether  to  the  first  two,  shake  again  ( ?),  and  describe  care- 
fully what  seems  to  have  happened.  Can  you  deduce  from 
this  the  relative  solubility  of  iodine  in  the  three  solvents  ? 


CHAPTER  VIII. 

CHLORINE  AND  HYDROGEN  CHLORIDE. 

1.  PREPARATION  OF  CHLORINE  [HOOD]. 
Experiments  1,  b  and  2  must  be  accomplished  at  one 
exercise.     1,  a  may  be  postponed  to  facilitate  this. 

a.  Prepare  some  strips  of  filter  paper  by  dipping  them  in 
starch  emulsion  to  which  one  drop  of  potassium  iodide  solu- 
tion has  been  added. 

Place  small  quantities  of  potassium  chlorate,  minium, 
litharge,  and  potassium  dichromate  in  as  many  test-tubes,  and 
add  a  little  concentrated  hydrochloric  acid  to  each.  Hang  a 
strip  of  the  prepared  paper  in  each  tube  ( ?)  and  notice  also 
the  odor  (?).  If  no  action  takes  place  in  the  cold,  apply  heat. 
What  property  is  common  to  the  substances  which  cause  the 
production  of  chlorine?  Can  you  lay  your  finger  on  the  cause 
of  the  difference  in  the  behavior  of  the  two  oxides  of  lead? 

b.  Arrange  a  250  c.c.  generating  flask  (Fig.  10)  and  a  bottle 
to  wash  the  gas,  like  that  in  Fig.  12.    Use  glass  tubes  with  the 
shortest  possible  rubber  connections  here  and  in  3,  d  (hydrogen 
chloride),  as  rubber  tubing  is  destroyed  by  these  gases.     Test 
the  apparatus  to  see  that  it  is  air-tight.    Charge  the  flask  by 
placing  in  it  a  large  handful  of  coarsely  powdered  [Iron  mortar] 
manganese  dioxide  and  enough   concentrated   hydrochloric 
acid  to  cover  the  dioxide.    Fill  the  washing  bottle  one-third 
(not  more)  full  of  water  (use  of  this?).    Notice  what  happens 
in  the  cold  before  applying  heat.    Use  a  shallow  vessel  filled 
with  boiling  water  (why  not  a  sand  bath  or  naked  flame?)  to 
warm  the  flask.    Fill  three  bottles  and  one  test-tube  with  the 
gas  by  downward  displacement,  covering  them  during  the 
process  with  a  card  perforated  to  admit  the  .tube  [See  note 
below].    The  experiments  described  in  2  should  be  begun  as 
soon  as  one  bottle  is  full.    Under  what  conditions  could  you 
collect  the  gas  over  water  [R]?    Give  some  of  the  reasons  for 
the  slowness  of  the  action,  remembering  that  the  manganese 
dioxide  is  insoluble  in  water. 

When  sufficient  chlorine  has  been  collected,  filter  a  part 
of  the  residue  in  the  flask  into  an  evaporating-dish,  evaporate 
to  dryness  [Hood],  and  redissolve  in  about  100  c.c.  of  boiling 
water  in  a  beaker.  If  the  residue  was  yellow,  from  the  pres- 

30 


CHLORINE  AND  HYDROGEN  CHLORIDE 


31 


ence  of  ferric  chloride,  add  sodium  hydroxide  solution  drop 
by  drop  to  the  boiling  liquid.  The  precipitate  will  at  first  be 
brown  ( ?)  Stop  as  soon  as  the  fresh  formations  of  precipitate 
are  white  ( ?).  Boil  vigorously  for  a  few  minutes,  filter  with 
the  assistance  of  a  water  pump  [See  note],  evaporate  the 
filtrate  to  one-fourth  of  its  former  bulk,  and  set  it  aside  to 
crystallize  (?).  Keep  the  product  for  use  in  3,  a.  If  pink 
crystals  are  not  obtained,  the  manganese  may  have  been  pre- 
cipitated along  with  the  iron.  In  that  case  the  precipitate, 
which  should  be  kept  as  a  matter  of  precaution,  may  be  re- 
dissolved  in  hydrochloric  acid  and  the  precipitation  repeated. 


Fig.  13. 

Notes. —  Be  careful  not  to  allow  any  of  the  gas  to  escape  into 
the  room.  When  the  gas  is  not  being  collected,  let  it  bubble  into 
caustic  soda  solution  in  a  test-tube.  Empty  the  flask  and  bottle 
finally  into  the  sink  in  the  hood. 

Much  time  may  be  saved,  and  better  results  obtained,  by 
using  a  pump  in  filtering  liquids  and  in  washing  precipitates. 
The  apparatus  is  shown  in  Fig.  13.  Use  a  small  cone  made  of  per- 
forated parchment  paper  to  protect  the  point  of  the  filter  paper. 
The  pump,  the  safety  bottle  for  protecting  the  solution  from  ad- 
mixture with  water  from  the  pump,  and  the  connecting  tubes 
may  be  obtained  from  the  storeroom  [Temp,  order]. 

2,  PROPERTIES  OF  CHLORINE  [Hood]. 

a.  In  one  bottle  of  the  gas  scatter  a  pinch  of  finely  pow- 
dered antimony  ( ?)  [R]. 

b.  Take  a  clean  piece  of  sodium,  cut  from  it  with  a  sharp 
knife  a  very  thin  slice  about  half  an  inch  square  (fingers  and 
knife  used  in  handling  it  must  be  dry!),  and  introduce  it  into 
a  bottle  of  chlorine  ( ?).     Cover  the  bottle  with  a  glass  plate 
and  examine  after  the  action  is  over.     Dissolve  the  deposit  in 


32       CHLOKINE  AND  HYDROGEN  CHLORIDE 

2  c.c.  of  water,  allow  it  to  crystallize  on  a  watch  glass,  and 
examine  with  a  lens  (?). 

c.  Connect  a  glass  tube,  terminating  in  a  capillary  open- 
ing, with  the  illuminating  gas  supply,  and  lower  a  small, 
burning  gas  jet  into  the  third  bottle  (?).     .Blow  the  breath 
into  the  bottle  after  withdrawing  the  jet  (?). 

d.  Fill  a  test-tube  with  hydrogen  from  a  Kipp's  apparatus. 
Bring  this  mouth  to  mouth  with  a  tube  of  chlorine  and  mix 
the  gases  by  repeated  inversion.    (Take  care  not  to  expose 
the  mixture  to  direct  sunlight.)    Hold  the  mouth   of  each 
tube  to  the  Bunsen  flame  ( ?). 

3.  PREPARATION  OF  HYDROGEN  CHLORIDE. 

a.  [Hood.]   Place  small  quantities  of  ammonium  chloride, 
barium  chloride,  mercuric  chloride,  and  manganous  chloride 
(obtained  in  1,  6)  in  as  many  test-tubes,  and  add  a  few  drops 
of  concentrated  sulphuric  acid  to  each.     Describe  what  hap- 
pens in  each  case.     Blow  moist  air  across,  the  mouth  of  the 
test-tube    (?).     Lower    a  glass    rod   dipped  in  ammonium 
hydroxide   solution  into    each   [See  note  below].     Try  the 
effect  of  heating.     Remember  that  the  solubility  (physical)  of 
the  substance  in  sulphuric  acid  will  largely  determine  the 
speed  of  the  action.     In  case  of  difficulty,  therefore,  powder 
the  substance  finely  and  shake  with  the  acid  for  some  minutes 
before  heating  and  testing. 

Note. — The  use  of  ammonia  is  not  a  specific  test  for  hydrogen 
chloride.  This  gas  can  be  employed  only  for  ascertaining  the 
presence  or  absence  of  any  one  of  several  gases  which  are 
capable  of  uniting  with  ammonia. 

b.  To  a  pinch  of  finely  powdered  sodium  chloride  add  a 
strong  solution  of  phosphoric  acid  and  heat  if  necessary  ( ?). 
Test  with  ammonia  as  before.     The  above  remark  about  solu- 
bility applies  also  to  this  case. 

Why  is  hydrogen  chloride  displaced  completely  in  a  and 
b  by  these  acids  under  these  conditions  [R]  ?  In  answering 
consider  the  results  of  c  and  d. 

c.  To  a  concentrated  solution  of  sodium  hydrogen  sul- 
ihate  add  pure  [Side-shelf]  concentrated  hydrochloric  acid 

Add  the  acid  a  very  little  at  a  time  to  avoid  over-rapid 
precipitation,  and  agitate  between  additions  The  longer  the 
operation  takes  the  better.  Examine  the  result  with  a 
lens(f). 

Relate  this  action  to  that  in  d,  and  consider  both  facts  in 
answering  the  question  in  b. 

d.  [Hood.]  In  a  250  c.c.  flask,  fitted  with  dropping-funnel, 


CHLORINE  AND  HYDROGEN  CHLORIDE       33 

gas  washing  bottle  containing  sulphuric  acid,  and  glass  de- 
livery tube,  place  a  handful  of  common  salt.  Admit  concen- 
trated sulphuric  acid  through  the  funnel.  Collect  the  gas  in 
three  dry  bottles  by  downward  displacement.  Attach  a  nozzle 
to  the  tube  and  prepare  an  aqueous  solution  for  use  in  4,  by 
passing  the  gas  through  10  c.c.  of  water  in  a  test-tube. 
Relate  this  action  to  that  in  c. 

4,  PROPERTIES  OF  HYDROGEN  CHLORIDE  AND  HYDROCHLORIC 
ACID  [HoodJ. 

a.  Invert  one  of  the  bottles  of  the  gas  in  the  pneumatic 
trough  ( ?).     Relate  this  property  to  that  observed  on  blowing 
moist  air  into  the  gas  (3,  a).     If  any  gas  remains,  what  should 
you  expect  it  to  be?     Test  your  conclusion  experimentally. 

b.  Pour  a  little  ammonium  hydroxide  solution  on  a  slip  of 
filter  paper  and  plunge  it  into  the  second  bottle  ( ?). 

Which  of  the  kinds  of  chemical  change  does  this  illus- 
trate? 

c.  Devise  a  way  of  proving,  in  a  rough  way,  that  the  gas 
is  heavier  than  air,  and  use  the  third  bottleful  for  carrying  it 
out. 

d.  Divide  the  aqueous  solution  into  three  parts.     To  the 
first  add  a  piece  of  zinc  (?).    To  the  second  add  some  sodium 
carbonate  solution  ( ?). 

Why  is  carbonic  acid  displaced  completely  by  the  hydro- 
chloric acid  [R]? 

Dilute  the  third  part  with  an  equal  volume  of  water  and 
distribute  it  between  four  test-tubes.  To  the  first  add  blue 
litmus  solution  or  paper  (?);  to  the  second  a  drop  of  silver 
nitrate  solution  (?);  to  the  third  a  drop  of  mercurous  nitrate 
solution  (?);  to  the  fourth  a  drop  of  lead  nitrate  solution  (?). 
After  the  last  three  mixtures  have  settled,  pour  away  the 
liquid,  add  water,  and  boil  the  precipitate  with  it  ( ?).  After- 
ward examine  the  liquids  when  they  have  become  cold  (?) 


CHAPTER  IX. 


THE   ATMOSPHERE,  NITROGEN,  AND  AMMONIA. 

1.  CONSTITUENTS  OF  AIR. 

a.  Place  a  large  plug  of  copper  turnings  in  the  center  of 

a  hard  glass  tube  about  25  cm.  long.     Fit  with  corks  and 

short  glass  tubes,  and  connect  with  the  short  tube  of  the 

aspirator.    Fill  completely  with  water  the  bottle  and  long 

,..»...  tube  of  the  aspirator  and  close 

•  »•"]  with  a  screw  clamp.     Arrange  a 

vessel  to  catch  the  water  dis- 
charged. Now  heat  the  copper 
red-hot  and  then  partly  open  the 
clamp  so  as  to  allow  the  water 
to  be  siphoned  off  in  a  slow 
stream.  The  air  will  pass  over 
the  heated  copper.  What 
change  does  the  copper  undergo 
and  what  collects  in  the  bottle? 
After  three-fourths  of  the  water 
has  run  out,  close  the  clamp,  dis- 
connect the  hard  glass  tube,  at- 
tach a  delivery  tube  in  its  place, 
elevate  the  end  of  the  siphon, 
and  insert  a  small  funnel.  Pour 
water  into  the  funnel  and  drive 
the  gas  over  into  a  bottle  of  water 
inverted  in  the  pneumatic  trough. 
Ascertain  whether  this  gas  sup- 
ports combustion.  Describe  the 
gas  as  regards  color  and  smell. 
Other  ways  of  removing  oxy- 
gen from  the  air  are  described 
elsewhere  (Chap.  IV,  5,  and  in  b). 


Fig.  14. 


b.  PROPORTION  OF  OXYGEN  TO  NITROGEN  BY  VOLUME  [Quant.]. 
(From  Cooley's  Laboratory  Studies.  Anpther  method  under 
nitric  oxide,  p.  66,  1,  c.) 

The  apparatus  (Fig.  14)  consists  of  a  large  test-tube  closed 
with  a  doubly  bored  rubber  stopper,  through  which  pass  a 
piece  of  glass  rod  and  a  short  glass  tube  terminating  in  a 

34 


THE    ATMOSPHERE,    NITROGEN,    AND    AMMONIA        35 

nozzle.  The  latter  projects  but  little  beyond  the  stopper. 
The  glass  tube  is  connected  with  a  funnel  by  means  of  a  rub- 
ber tube  15  cm.  long,  which  can  be  closed  with  a  spring  clamp. 
The  stem  of  the  funnel  may  be  held  in  a  clamp  on  the  ring 
stand.  Disconnect  the  test-tube,  remove  the  piece  of  glass 
rod,  pour  the  prepared  alkaline  solution  of  pyrogallic  acid1 
into  the  funnel,  and  open  the  spring  clamp  slightly  so  as  to 
allow  the  solution  to  fill  the  entire  rubber  tube  and  nozzle. 
Push  the  rubber  stopper  tightly  into  the  test-tube  and  then 
insert  the  glass  rod  and  thus  inclose  a  volume  of  air  equal  to 
the  content  of  the  test-tube  and  at  the  pressure  of  the  atmos- 
phere. During  these  operations,  which  should  be  performed 
as  quickly  as  possible  to  avoid  exhaustion  of  the  solution  by 
absorption  of  oxygen  from  the  air  of  the  room,  do  not  warm 
the  test-tube  by  handling.  Now  open  the  clamp  and  allow  the 
liquid  to  enter.  It  will  flow  in  until  the  oxygen  is  all  ab- 
sorbed. Keeping  the  clamp  open,  invert  the  test-tube  and 
equalize  the  level  of  the  liquid  in  both  vessels ;  then  close  the 
clamp,  restore  the  test-tube  to  its  original  position,  and  mark 
the  levels  of  the  liquid  and  the  bottom  of  the  stopper  by 
means  of  rubber  rings. 

Disconnect  the  test-tube,  wash  out  the'  liquid,  and  ascer- 
tain the  volume  marked  off  by  each  ring  by  weighing  water. 
The  smaller  is  that  of  the  oxygen,  the  larger  that  of  the  air. 
Calculate  the  percentage  composition  of  air  by  volume. 

c.  Place  some  clear  barium  hydroxide  solution  in  the  bot- 
tom of  a  beaker  and  leave  it  exposed  to  the  air  for  some 
hours  ( ?)     What  substances  are  found  in  the  air  besides  those 
examined  here  [R]  ? 

d.  The  weight  of  1  liter  of  air,  or  of  oxygen,  or  nitrogen, 
may  be  measured  by  the   method  described   under  carbon 
monoxide,  p.  77,  9. 

2.  NITROGEN.  Place  about  8  g.  of  sodium  nitrite  and  3 
g.  of  ammonium  chloride  in  a  250  c.c.  flask,  add  about  15  c.c. 
of  water,  and  clamp  the  flask  by  the  neck.  Warm  gently 
[Caution]  and  collect  the  g-as  in  a  bottle  over  water,  after 
time  has  been  given  for  the  displacement  of  the  air  in  the 
flask.  Have  an  evaporating-dish  filled  with  cold  water  in 
readiness  and  bring  it  up  over  the  bottom  of  the  flask  when 
the  action  becomes  too  violent. 

Ascertain  whether  this  gas  supports  combustion,  and  de- 
scribe it  as  regards  color  and  smell.  What  impurity  causes 

1  Prepared  by  dissolving  5  g.  of  pyrogallic  acid  in  15  c.c.  of 
water  and  adding  a  solution  of  120  g.  of  potassium  hydroxide  in 
88  c.c.  of  water. 


36         THE    ATMOSPHERE,    NITROGEN,    AND    AMMONIA 

the  slight  odor?    With  what  substances  will  nitrogen  unite 
directly  [R]? 

3.  AMMONIA.    Provide  a  small  flask  connected  with  a  plain 
U  tube.    Place  a  little  water  in  the  bend  of  the  latter  so  as  to 
close  the  passage.     Put  into  the  flask  a  mixture  of  powdered 
quicklime  and  ammonium  chloride,  and  heat  (?).    Preserve 
the  solution  of  ammonium  hydroxide.    This  reaction  between 
strong  bases  and  ammonium  salts  is  used  as  a  test  for  the 
latter. 

What  method  would  you  pursue  if  you  were  asked  to  de- 
termine the  weight  of  a  liter  of  ammonia  gas  ?  How  is  the 
composition  of  ammonia  by  volume  determined  [Lect.]? 

4.  AMMONIUM  HYDROXIDE. 

a.  Wash  a  piece  of  red  litmus  paper  with  water,  dip  it  in 
the   solution  ( ?)  and  expose  it  to  the  air  for  some  time  ( ?). 
Dip  a  piece  of  blue  litmus  paper  in  dilute  hydrochloric  acid  ( ?) 
and  expose  it  to  the  air  for  the  same  length  of   time  ( ?). 
Compare  the  results  and  interpret.     Hold  a  rod  dipped  in 
concentrated  hydrochloric  acid  over  the  solution  ( ?). 

b.  Place  a  little  of  the  solution  in  an  evaporating-dish  and 
leave  it  exposed  to  the  air  for  twenty-four  hours,  noticing  the 
odor  from  time  to  time  (?).     In  a  second  evaporating-dish 
warm  some  of  the  solution  and  notice  the  odor  from  time  to 
time  [Hood]  (?). 

c.  Neutralize  the  rest  of  the  solution  with  dilute  sulphuric 
acid  and  evaporate  to  dryness  ( ?).     Scrape  out  the  residue 
and  heat  it  strongly  on  the  inverted  lid  of  a  crucible  ( ?). 

After  completing  Chap.  XII,  enumerate  the  things  which 
a,  6,  and  c  show  the  solution  of  ammonia  to  contain.  Explain 
fully  the  mechanism  of  the  changes  in  b  and  c. 

d.  Place  some  ammonium  chloride  in  the  middle  of  an 
open,  hard  glass  tube.    Support  this  in  a  very  slightly  inclined 
(5°)  position,  put  a  moist  piece  of  neutral  litmus  paper  (or  a 
piece  of  each  color)  in  each  end.  and  heat  the  salt  strongly 
(?).     Watch  closely  the  effect  on  each  test-paper  (?).     What 
is   the  action  of  heat  on  ammonium  chloride?     Which  gas 
appeared  first  at  the  ends  of  the  tube,  and  why  first  at  both 
lower  and  higher  ends  ?    Has  gravity  any  influence  on  the 
result  ? 


CHAPTER  X. 

BROMINE,  IODINE,  AND  FLUORINE,  AND  THEIR  COMPOUNDS  WITH 
HYDROGEN. 

1.  PREPARATION  OF  BROMINE  AND  IODINE. 

Note. —  Chlorine  and  the  elements  studied  in  this  chapter 
form  a  group  having  very  similar  properties,  and  are  called  the 
halogens.  Recall  the  facts  about  chlorine  and  hydrogen  chloride 
(Chap.  VIII)  and  use  them  as  a  guide  in  trying  to  understand  the 
chemistry  of  the  rest  of  the  group.  Remember  particularly  that 
chlorine  is  colored,  has  a  powerful  odor,  and  does  not  cause  fumes 
in  moist  air;  and  that  hydrogen  chloride  is  colorless  and  causes 
dense  fumes  in  moist  air.  The  corresponding  substances  through- 
out the  group  may  be  expected  to  present  properties  like  these. 
The  hydrogen  compounds,  hydrogen  chloride,  hydrogen  bromide, 
etc.,  are  known  as  the  hydrogen  halides. 

a.  For  the  action  of  manganese  dioxide  on  hydrobromic 
and  hydriodic  acids  (cf.  Chap.  VIII,  1,  6,  p.  30)  see  5  and  6. 

b.  Powder  about  1  g.  each  of  the  bromide  and  iodide  of 
of  potassium,  mix  them  in  separate  test-tubes  with  the  same 
weight  of  powdered  manganese  dioxide,  and  moisten  each 
with   concentrated   sulphuric   acid.     Warm   very  gently  (?). 
How  does  a  fluoride  behave  under  these  circumstances,  and 
why  [R]?     Answer  the  same  question  in  regard  to  chlorides 
(Chap.  VIII,  3,  a,  and  1,  6,  pp.  32  and  30). 

What  have  you  ascertained  about  the  solubilities  of  iodine 
(Chap.  VII,  7,  e,  p.  29)?  The  relative  solubilities  of  bromine 
are  similar. 

2.  THE  HYDROGEN    HALIDES  I     PRELIMINARY    [Hood]. 

a.  Powder  about  a  gram  of  iodide  of  potassium,  place  it  in 
a  test-tube,  and  moisten  it  with  concentrated  sulphuric  acid  ( ?). 
Warm,  if  necessary.  Investigate  the  result,  which  furnishes 
a  mixture  of  gases,  as  follows: 

a.  Breathe  across  the  mouth  of  the  test-tube  to  ascertain 
the  effect  of  the  gas  on  moist  air.  What  gas  previously  made 
showed  the  same  behavior?  Remembering  the  similarity 
between  the  halogens  and  between  their  corresponding  com- 
pounds, what  do  you  infer  in  this  case?  To  confirm  this  con- 
clusion, lower  a  glass  rod  dipped  in  ammonium  hydroxide 
solution  into  the  test-tube  (?);  also  a  strip  of  filter  paper 
dipped  in  lead  nitrate  solution  (?)  [R]. 

37 


38          BROMINE,  IODINE,  AND  FLUOBINE 

(3.  What  is  the  color  of  the  gas,  or  any  part  of  it  ?  What 
is  the  colored  body?  Was  there  any  corresponding  product 
when  sulphuric  acid  acted  on  a  chloride?  By  what  kind  of 
chemical  action  could  this  colored  substance  be  formed  from 
the  one  identified  in  a  ? 

y.  Study  the  odor  of  the  gas  and  describe  it  (?).  Was 
there  any  effect  on  the  lead  nitrate  which  remained  unex- 
plained in  a?  Can  you  now  explain  it  [R]? 

The  work  in  a  and  /3  leads  to  the  recognition  of  two  dis- 
tinct gaseous  products.  That  in  y  will  yield  one,  and  perhaps 
two  others.  Still  another  distinct  solid  product  may  be  ob- 
served on  the  walls  of  the  tube  ( ?).  Construct  separate  equa- 
tions representing  the  formation  of  the  first  product  from  the 
original  materials,  and  of  each  of  the  others  from  this  product 
and  sulphuric  acid.  What  two  properties  of  sulphuric  acid 
and  what  property  of  hydrogen  iodide  are  illustrated  by  this 
set  of  experiments? 

b.  Repeat  the  work  in  a,  using  powdered  potassium  bro- 
mide instead  of  the  iodide,  and  answer  the  same  questions, 
substituting  the  words  bromine  and  bromide  everywhere  for 
iodine  and  iodide. 

v  c.  Cover  a  square  of  glass  with  a  thin  layer  of  paraffin  by 
warming  it  very  cautiously  far  above  a  Bunsen  flame  and 
rubbing  it  on  one  side  with  solid  paraffin.  Moisten  about  3 
g.  of  fluorspar  in  a  leaden  dish  [Temp,  order]  with  concen- 
trated sulphuric  acid  (do  not  cover  with  the  acid).  Remove 
part  of  the  paraffin  from  the  glass  by  drawing  some  design 
with  the  end  of  a  file,  thus  exposing  part  of  the  glass  to  the 
action  of  the  vapor.  Place  the  glass  on  the  top  of  the  leaden 
dish  and  set  the  whole  above  a  radiator,  at  such  a  distance 
that  the  dish  will  be  warmed  without  risk  of  the  paraffin  being 
melted.  After  half  an  hour  warm  the  glass  once  more  and 
wipe  the  paraffin  off  with  a  piece  of  filter  paper  (?).  Write 
equations  representing  the  action,  and  state  what  becomes  of 
each  of  the  constituents  of  the  glass  [R].  Try  the  test  of  a 
rod  dipped  in  ammonium  hydroxide  solution  and  held  over 
the  contents  of  the  lead  dish  (?).  Is  there  any  odor  or  action 
on  paper  dipped  in  lead  nitrate  solution,  indicating  reduction 
of  the  sulphuric  acid,  similar  to  that  caused  by  hydrogen 
iodide  or  bromide? 

How  does  a  chloride  behave  under  similar  circumstances  ? 
What  difference  between  the  four  hydrogen  halides  do  the 
results  in  a,  6,  and  c  bring  to  light  ?  Arrange  the  hydrogen 
halides  in  the  order  of  their  stability  toward  oxidizing  agents, 
so  far  as  your  experiments  enable  you  to  judge  of  this. 


BROMINE,    IODINE,    AND    FLUORINE 


39 


d.  Take  small  samples  of  finely  powdered  bromide  and 
iodide  of  potassium  in  separate  test-tubes,  cover  each  with 
concentrated  phosphoric  acid  solution,  and  agitate  for  some 
time  ( ?).  Note  the  apparent  slowness  of  the  action  on  account 
of  the  insolubility  (physical)  of  the  salts  in  this  liquid  (the 
sodium  salts  might  be  substituted  with  advantage,  as  they  are 
much  more  soluble).  Warm,  if  necessary.  Observe  the  odor 
and  apply  the  ammonia  ( ?)  and  lead  nitrate  tests  ( ?)  as  above. 
What  difference  between  the  actions  of  sulphuric  and  phos- 
phoric acids  do  you  observe?  What  do  you  infer  in  regard 
to  the  properties  of  these  acids? 


Fig.  15. 

3.  PREPARATION  OF  HYDROGEN  BROMIDE  AND  IODIDE  [Hood]. 

a.  Fit  up  a  250  c.c.  flask  with  a  dropping- funnel  and  tube, 
and  connect  with  a  U  tube  (Fig.  15).     Fill  the  latter  with  dry, 
broken  glass,  or  porcelain,  mixed  with  a  little  red  phosphorus 
(why  ?).     Connect  the  other  limb  of  the  U  tube  with  a  second, 
larger  U  tube  [Temp,  order]  containing  about  10  c.c.  of  water. 
Place  about    5  g.  of  red  phosphorus  mixed  with  twice  its 
weight  of  sand  in  the  flask,  add  5  c.c.  of  water,  and  mix  by 
shaking.     Pour  into  the  globe  of  the  funnel  about  8  c.c.  of 
bromine.     Allow  the  bromine  to  flow  drop  by  drop  on  to  the 
phosphorus,  and  let  the  gas  dissolve  in  the  water  in  the  second 
U  tube.     Record  such  properties  of  the  gas  as  you  observe. 
Keep  the  solution  for  use  in  4,  a  and  6. 

b.  Hydrogen  iodide  may  be  made  in  the  same  way,  except- 
ing that  the  iodine  and  phosphorus  (in  the  proportion  of  11:1 
by  weight)  are  first  intimately  mixed  in  a  mortar  and  are  then 
placed  in  the  flask,  and  the  water  is  allowed  slowly  to  drop 
upon  them  from  the  funnel. 


40  BROMINE,    IODINE,    AND    FLUOfclNE 

4.  DISPLACEMENT  OF  HALOGENS   BY  EACH   OTHER     [Hood]. 
Prepare  a  little  chlorine  (p.  30,  1,  6)  in  a  side-neck  test-tube, 
fitting  the  latter  with  a  tube  bent  at  right  angles. 

a.  Pass  a  few  bubbles  of  chlorine  into  a  diluted  (1:10) 
solution  of  potassium  bromide  in  a  test-tube  ( ?).  Add  a  drop 
or  two  of  the  liquid  to  a  test-tube  full  of  starch  emulsion  (?). 
Add  a  little  chloroform  or  ether  to  the  remainder  of  the  liquid 
and  shake  (?).  Explain  (see  notes).  Pass  a  few  bubbles  of 
chlorine  through  a  small  portion  of  the  solution  of  hydrogen 
bromide  obtained  in  3,  a  ( ?). 

6.  In  like  manner  pass  a  few  bubbles  of  chlorine  through 
a  very  highly  diluted  solution  of  potassium  iodide  (?).  Add 
a  few  drops  of  the  liquid  to  a  test-tube  full  of  starch  emul- 
sion (?).  Add  a  little  chloroform  or  ether  to  the  remainder  of 
the  liquid  and  shake  (?).  Explain.  In  case  the  aqueous 
solution  remains  brown  (why  ?  R)  use  a  little  more  chlorine 
and  shake  again  ( ?). 

c.  Examine  the  action  of  bromine  water  on  highly  diluted 
potassium  iodide  solution  in  exactly  the  same  way  ( ?). 

Notes. — When  layers  of  different  colors  appear  in  a  test-tube, 
always  mix  the  materials  by  inverting  the  tube  once  or  twice 
before  drawing  conclusions.  The  contents  of  the  whole  test-tube 
should  be  made  as  homogeneous  as  possible. 

Chloroform  and  ether  have  no  chemical  action  on  bromine  or 
iodine  ;  they  simply  dissolve  them  more  readily  than  water  does. 

5.  DISPLACEMENT  OF  SULPHUR  AND  OXYGEN  BY  THE  HALOGENS 
AND  BY  EACH  OTHER. 

a.  Place  2-3  c.c.  of  diluted  sodium  sulphide  solution  in  a 
test-tube  and  add  bromine  water  ( ?). 

6.  [Hood.]    Place  5  g.  of  powdered  iodine  with  50  c.c.  of 
water  in  a  small  flask  provided  with  a  cork  and  a  tube,  bent  at 
right  angles  and  extending  to  the  bottom.   Pass  hydrogen  sul- 
phide from  a  Kipp's  generator  through  the  mixture,  loosening 
the  cork  once  or  twice  at  first  to  permit  the  air  to  be  displaced 
by  the  gas,  until  the  iodine  is  all  gone  and  the  solution  no 
longer  becomes  brown  on  being  shaken.     Agitate  constantly 
to  hasten  the  process.     Describe  what  happens.     Warm  and 
filter  the  solution. 

Obtain  a  distilling  flask  and  condenser  [Temp,  order]  and 
distil  the  filtrate  fractionally  (Fig.  16),  collecting  first  the 
part  that  comes  over  at  100%  then  the  parts  boiling  between 
100-103°,  103-106°,  and  so  forth.  Use  a  very  small  flame  and 
be  careful  not  to  allow  it  to  reach  the  walls  of  the  flask  above 
the  liquid  or  breakage  will  take  place  A  large  flame  may  not 
only  crack  the  flask,  but  may  also  cause  the  thermometer  to 


BKOMINE,    IODINE,    AND    FLUORINE 


41 


show  a  higher  temperature  than  it  could  acquire  from  the 
vapor  alone.  Stop  when  the  liquid  is  nearly  all  distilled  off. 
Note  the  highest  temperature  reached.  Pour  the  residue 
into  a  test-tube  and  keep  the  series  for  use  in  7. 

What  substance  causes  the  color  of  the  higher  fractions 
and  of  the  residue? 

Recall  the  action  of  chlorine  on  water  in  sunlight.  What 
is  the  action  of  fluorine  on  water  [R]?  In  what  way  do  these 


Fig.  16. 


resemble  the  action  of  iodine  on  hydrogen  sulphide?  What 
is  the  action  of  oxygen  on  hydrogen  sulphide  solution[R]? 
What  is  its  action  on  hydrogen  iodide  solution  [R]  ? 

6.  PROPERTIES  OF  AQUEOUS  HYDROBROMIC  ACID.     Divide  the 
solution  into  six  portions  and  examine  its  behavior  toward 
(a)  litmus,  (b)  zinc  in  contact  with  a  platinum  wire,  (c)  silver 
nitrate  solution,  (d)  mercurous  nitrate  solution,  (e}  lead  nitrate 
solution,  (/)  powdered  manganese  dioxide  (warm).     Boil  c,  d 
and  e,  after  pouring  away  the  supernatant  liquid  and  adding 
more  water  to  each  (?).    Compare  these  results  with  those 
found  in  the  case  of  hydrochloric  acid,  (p.  33, 4,  d). 

The  solution  is  as  good  a  conductor  of  electricity  as  that 
of  hydrogen  chloride.  What  conclusion  do  we  draw  from 
this  LR-,  p,  47  1,  e]? 

7.  PROPERTIES    OF   AQUEOUS    HYDRIODIO   ACID.     Add  silver 
nitrate  solution  to  each  of  the  fractions  obtained  in  5,  using 


42  BROMINE,    IODINE,    AND   FLUORINE 

only  a  part  of  the  liquid  in  the  case  of  the  two  with  the  high- 
est boiling  points.  At  what  temperature  did  the  most  con- 
centrated solution  of  hydrogen  iodide  come  over?  What 
peculiarity  of  aqueous  hydriodic  acid  does  the  result  indicate? 
What  other  solutions  show  the  same  peculiarity?  Compare 
with  the  behavior  of  ammonia  (p.  36,  4,  6). 

Place  a  piece  of  zinc,  in  contact  with  a  platinum  wire,  in 
the  remainder  of  one  of  the  higher  fractions  ( ?).  Test  the 
other  with  litmus  paper  ( ?),  and  then  add  powdered  man- 
ganese dioxide  and  warm  ( ?). 

8.  IDENTIFICATION  OF  HALOGEN  COMPOUNDS.  On  the  basis 
of  the  experiments  in  this  chapter,  devise  a  system  of  tests 
which  would  enable  you  to  distinguish  between  chlorides 
bromides,  iodides,  and  fluorides. 


CHAPTER  XL 

OXYGEN  COMPOUNDS  OF  THE  HALOGENS.   OZONE  AND  HYDROGEN 
PEROXIDE. 

1.  HYPOCHLOROUS  ACID  AND  HYPOCHLORITES.     Fit  up  a  chlo- 
rine apparatus  capable  of  delivering  a  large  amount  of  chlo- 
rine.    Use  a  gas  washing  bottle  (why?)  containing  a  small 
(why?)  amount  of  water.     Use  the  same  source  of  chlorine  in 
1,  3,  and  5,  a. 

a.  Make  an  aqueous  solution  of  chlorine  in  a  test-tube. 
Retain  a  few  drops  of   this  for  use  in  b  and  place  in  the 
remainder  some  litmus  paper,  paper  with  printing  and  pen  and 
pencil  marks  upon  it,  and  a  piece  of  colored  calico.     Observe 
the  effect  on  each.     Explain  [R]. 

b.  To  a  few  drops  of  chlorine  water  add  a  drop  of  indigo 
solution  ( ?). 

c.  Slake  a  piece  of  quicklime  in  a  small  beaker  and  add 
enough  water  to  make  a  thin  paste.     Pass  chlorine  into  the 
mixture  for  ten  or  fifteen  minutes  (?),  cooling  the  vessel  by 
surrounding  it  with  water  (why?)  and  stirring  the  contents 
during  the  process.     Thoroughly  soak  a  piece  of  litmus  paper 
(?)  and  a  piece  of  colored  calico  (?)  in  the  paste  and  then  place 
them  in  dilute  sulphuric  acid  (?).     Repeat  this  treatment  of 
the  litmus  and  calico  if  necessary. 

How  could  you  make  a  solution  of  pure  calcium  or  potas- 
sium hypochlorite  [R]  ? 

2.  NASCENT  ACTION.   Dilute  some  potassium  permanganate 
solution  with  water,  and  add  an  equal  volume  of  dilute  sul- 
phuric acid  to  it.    Divide  into  two  parts.    Through  one  pass  a 
stream  of  hydrogen  gas  from  a  Kipp's  apparatus  (?).     To  the 
second  add  some  zinc  dust  (?).     Interpret  the  result. 

3.  CHLORATES   [Hood].      Dissolve   about   3  g.  of   solid 
potassium  hydroxide  in  7  c.c.  of  water  in  a  test-tube  and  sat- 
urate (test  ?     The  solution  must  cease  to  feel  soapy)  the  hot 
solution  with  chlorine.     Crystals  will  appear  during  the  pro- 
cess and  will  increase  in  quantity  when  the   liquid  cools. 
Describe  the  crystals.     Filter,  acidify  (test?)  the  filtrate  with 
pure  nitric  acid,  and  test  with  silver  nitrate  solution  ( ?).     Dry 
the  crystals,  heat  them  in  a  narrow  tube,  and  test  for  oxygen  (?). 

43 


44      OXYGEN  COMPOUNDS  OF  THE  HALOGENS 

To  potassium  chlorate  solution  add  silver  nitrate  solu- 
tion ( ?).  To  a  minute  amount  of  potassium  chlorate  add  a 
few  drops  of  pure,  concentrated  hydrochloric  acid  [R]  ( ?). 

4.  PERCHLORATES.     Measure  500  c.c.  of  water  into  your 
1 -liter  bottle,  and  mark  the  level  reached.     Observe  the  tem- 
perature and  pressure  of   the  air  and  calculate  the  weight  of 
potassium  chlorate  which  will  be  necessary  to  give  this  volume 
of  oxygen  while  leaving  the  perch lorate  and  chloride  behind. 
This  stage  is  reached  when  one-fifth  of  the  total  oxygen  has 
been  evolved.     Weigh  this  quantity  of  chlorate  into  a  rather 
wide  hard  glass  test-tube  fitted  with  a  cork  and  delivery  tube. 
See  that  the  apparatus  is  air-tight.     Heat  the  chlorate  and 
drive  off  enough  gas  to  fill  the  bottle  to  the  mark  by  displace- 
ment.    Proceed  slowly  toward  the  end  so  as  to  allow  the  gas 
to  cool,  stop  heating  when  the  mark  is  reached,  and  remove  the 
tube  at  once  from  the  water.     Pour  the  melted  substance  into 
a  mortar  before  it  has  time  to  solidify.     Powder  the  mixture. 

To  separate  the  substances,  calculate  approximately  the 
amount  of  potassium  chloride  which  must  be  present,  and 
shake  the  powder  persistently  with  an  amount  of  cold  water 
just  sufficient  to  dissolve  it  (see  note).  Collect  the  undissolved 
material  on  a  filter  paper  just  large  enough  to  hold  it,  and 
wash  it  with  a  few  drops  of  cold  water.  Calculate  the  amount 
of  water  which  at  100°  will  dissolve  the  residue,  assuming  it 
to  be  potassium  perchlorate.  Dissolve  it  in  this  amount  of 
water  by  boiling,  and  allow  the  solution  to  stand  for  an  hour 
or  two.  Collect  the  crystals,  wash  them  as  before,  and  dry 
them  on  a  radiator. 

Dissolve  a  little  of  the  substance  in  distilled  water  and 
test  with  silver  nitrate  solution  ( ?). 

To  a  minute  amount  of  the  crystals  add  a  few  drops  of 
pure,  concentrated  hydrochloric  acid  ( ?).  How  could  you  dis- 
tinguish between  a  perchlorate  and  a  chlorate? 

Note. — The  solubilities  of  the  salts  are  as  follows: 

Grams  dissolved  by  10  c.c.  of  water. 

15°  20°  100° 

Potassium  chloride  3.3  3.5  5.6 

Potassium  perchlorate        0.15  0.18  2.0 

5.  BROMIO  AND  IODIC  ACIDS  [Hood]. 

a.  Take  two  test-tubes  and  place  in  each  5  c.c  of  water. 
Add  a  single  drop  of  potassium  iodide  solution  to  one,  and  a 
single  drop  or^  potassium  bromide  solution  to  the  other. 
Pass  chlorine,  a  few  bubbles  at  a  time,  into  them  alternately, 
shaking  after  each  addition  of  chlorine  ( ?).  Continue  until 
no  further  change  occurs.  Explain  the  changes  which  are 
observed  [R]. 


OZONE  AND  HYDROGEN  PEROXIDE         45 

b.  Take  2  c.c.  of  potassium  bromate  solution  in  a  test- 
tube,  add  an  equal  volume  of  pure,  dilute  sulphuric  acid  ( ?), 
and  divide  into  two  parts.  Allow  one  part  to  stand  to  see 
whether  there  is  any  further  action  ( ?).  To  the  other  part  add 
a  single  small  fragment  of  iodine  and  shake  for  several  min- 
utes ( ?).  Pour  the  solution  away  from  any  undissolved  iodine 
and  shake  the  former  with  a  few  drops  of  chloroform  ( ?).  (The 
chloroform  is  used  simply  as  a  solvent  which  collects  the  free 
halogen  from  dilute  silution  in  a  great  bulk  of  water).  Which 
of  these  halogens  has  the  greater  tendency  to  unite  with 
oxygen? 

6.  OZONE.     Place  two  or  three  pieces  of  phosphorus  in  a 
bottle,  add  enough  water  to  half  cover  them,  and  one  drop  of 
potassium  dichromate  solution.     Dip  a  strip  of  filter  paper  in 
starch  emulsion  to  which  a  drop  of  potassium  iodide  solution 
has  been  added.     Fasten  it  by  means  of  a  cork  in  such  a  way 
that  it  hangs  down  almost  to  the  phosphorus.     Allow  the  ap- 
paratus to  stand  for  an  hour  ( ?).     After  the  effect  appears  on 
the  starch  paper,  try  a  paper  dipped  in  manganous  sulphate 
solution  ( ?).     Return  the  phosphorus  to  the  supply  bottle. 

7.  PEROXIDES. 

a.  Dissolve  about  1  g.  of  sodium  peroxide  (how  is  this 
made?)  in  100  c.c.  of  cold  water  in  a  flask.     Add  this  amount 
of  the  oxide  a  very  little  at  a  time,  shaking  and  cooling  (why?) 
the  mixture  in  a  stream  of  water  during  the  process.     What 
does  the  solution  contain  [R]?     Add  to  it  a  little  dilute  sul- 
phuric acid  a  few  drops  at  a  time,  continuing  the  cooling. 
What  does  the  solution  now  contain?     Divide  the  mixture  into 
three  parts. 

b.  To  the  first,  placed  in  a  narrow  test-tube,  add  dilute, 
acidified  [c/.  p.  57,  3,  c]  potassium  permanganate  solution  (?). 
Test  the  gas  which  comes  off  for  oxygen,  if  the  quantity  is 
sufficient  for  the  purpose.     By  what  term  should  we  describe 
this  effect  of  hydrogen  peroxide? 

Add  the  second  portion  to  starch  emulsion  containing  a 
drop  of  potassium  iodide  solution  ( ?).  By  what  term  should 
we  describe  this  effect  of  hydrogen  peroxide? 

To  the  third  add  some  ether  (object  of  this  [R]?)  and 
shake,  and  then  add  one  drop  and  no  more  of  potassium 
dichromate  solution  and  shake  again  ( ?). 

c.  Suspend  lead  dioxide,  barium  dioxide,  and  manganese 
dioxide  separately  in  water  and  treat  with  dilute  sulphuric 
acid  as  in  a.    Filter  and  apply  to  each  filtrate  the  ether  and 
dichromate  test  as  in  b  (?).     What   are  the  differences  in 
behavior  and  constitution  between  a  true  peroxide  and  those 
oxides  which  are  sometimes  called  peroxides  [R]? 


CHAPTER  XII. 


IONIC   CHEMICAL    ACTIONS.      INTERACTIONS    OF   ACIDS,  BASES,  AND 

SALTS.1 

1.  IONIZATION.  How  do  we  ascertain  experimentally 
whether  a  substance  is  ionized  in  solution  or  not  and  learn 
the  extent  of  the  ionization  [R]?  The  degrees  to  which 
aqueous  solutions  of  many  substances  are  ionized  are  given  in 
a  table  in  the  Appendix.  Constant  reference  to  this  will  be 
necessary  in  interpreting  the  observations  in  this  and  succeed- 
ing chapters. 

The  experiments  of  paragraph  1  are  really  selected  from 
several  later  ones  and  are  performed  as  a  group,  since  the  same 
apparatus  serves  for  all.  They  may  be  postponed  if  a  set  of 
the  apparatus  is  not  available  at  the  moment. 

Obtain  [Temp,  order]  a  pair  of  electrolytic  cells  like  that 
in  Fig.  17,  and  half  fill  one  with  dilute  sulphuric  acid.  When 
the  cells   are  connected   in  series 
with  the  battery,  evolution  of  gas 
in  this  cell  will  indicate  that  the 
material  in  the  second  cell  is  a  con- 
ductor, and  that  the  circuit  is  there- 
fore   complete.      In    the   contrary 
case,  the  second  substance  is  a  non- 
conductor, or  at  all  events  a  very 
bad  conductor.    If  the  substance  in 
the  second  cell  is  a  solution,  what 
conclusion  may  be  drawn  in  regard 
to  the  condition  of  the  dissolved 
body  in  each  event  [R]  ? 
Half  fill  the  second  cell  with  the  substances  named  below 
in  turn.     See  very  particularly  that  the  electrodes  in  each  cell 
are  on  opposite  sides  of  the  glass  partition,  connect  with  the 
battery,  and  observe  the  effect  in  the  first  cell.     When  the 
same  experiment  has  been  shown  in  the  lecture-room,  the 
result  may  be  recorded  here  and  the  experiment  omitted. 
Wash  the  cell  and  electrodes  very  carefully  after  each  trial. 

1  Class-room  instruction,  illustrated  experimentally,  must  pre- 
cede and  accompany  the  work  in  this  chapter  or  little  will  be 
learned  from  it.  The  sign  for  reference  to  a  book  or  to  informa- 
tion obtained  in  lectures  [R],  has  been  used  very  little  in  this  chap- 
ter, as  the  dependence  on  these  sources  is  constant. 

46 


Fig.  17. 


INTERACTIONS   OF   ACIDS,    BASES,    AND    SALTS         47 

The  substances,  or  solutions,  in  a,  c,  d,  e,  /,  show  the 
behavior  typical  of  the  classes  of  substances,  or  their  solu- 
tions, to  which  each  example  belongs.  After  giving  the  result 
in  your  notes,  name  the  class  of  bodies  which  is  illustrated  in 
each  case. 

a.  Dry  crystallized  sodium  chloride. 
6.  Distilled  water. 

c.  Aqueous  solution  of  sodium  chloride. 

d.  Diluted  aqueous  solution  of  sodium  hydroxide. 

e.  Diluted  aqueous  solution  of  hydrochloric  acid. 
/.    Aqueous  solution  of  sugar. 

g.  Dry  the  cell  by  washing  first  with  alcohol  and  then 
with  ether  [Instructions].  Test  the  conductivity  of  a  solution 
of  dry  hydrogen  chloride  in  toluene  [Side-shelf].  What  dif- 
ference between  water  and  toluene  do  e  and  g  bring  to  light  ? 
Keep  the  solution  in  a  dry  test-tube  for  further  use  in  2,  d. 

h.  Subsequent  chemical  experiments  with  the  same,  or 
similar,  substances  or  solutions  will  bring  out  the  relation 
between  conductivity  and  chemical  behavior  and  its  explana- 
tion. 

The  chemical  composition  of  the  ions  into  which  any  com- 
pound is  split  is  ascertained  by  examining  the  substances  set 
free  at  the  electrodes  during  electrolysis  of  a  solution  and  by 
a  study  of  the  interactions  of  the  ions  in  the  solution.  The 
use  of  the  latter  method  is  illustrated  in  later  paragraphs. 

Solutions  which  show  exceptional  depression  of  the  freez- 
ing point,  are  decomposed  by  a  current  of  electricity,  and 
exhibit  certain  other  properties  capable  of  quantitative  corre- 
lation, are  called  electrolytes.  Substances  which,  when  dis- 
solved in  water,  furnish  electrolytes  are  called  ionogens.  Acids, 
bases,  and  salts,  and  no  other  compounds,  are  ionogens.  Solu- 
tions of  ionogens  in  water  are  mixtures  of  several  physical 
components.  These  components  are  related  in  sets  to  one 
another  through  chemical  equilibria.  For  example,  in  water 

alone  there  are  three  components  (H2O  ±5  H  +  OH),  in  hy- 
drochloric acid  there  are  five  components  in  two  sets  (H2O 

±5  H  +  OH  and  HC1  ±s  H  -f  Cl).  With  certain  restrictions 
each  component  of  such  a  solution  may  undergo  chemical 
change  independently  of  the  others. 

Give  a  complete  list  of  the  different  things  (eight  of  them) 
which  are  present  in  every  aqueous  solution  of  common  salt, 
distinguishing  those  which  are  present  in  large  from  those 
which  are  present  in  minute  quantity.  How  do  the  propor- 


48  IONIC   CHEMICAL    ACTIONS 

tions  of  each  of  these  things  vary  with  changes  in  the  concen- 
tration of  the  solution?  Which  of  the  eight  are  usually  most 
conspicuous  in  chemical  actions  involving  solutions  of  com- 
mon salt  [R]?  State  what  happens  when  these  most  active 
constituents  are  removed  from  the  scene  of  action  [R.  Lect.]. 
What  you  have  stated  about  common  salt  holds  mutatis 
mutandis  for  solutions  of  all  other  ionogens. 

2.  BASES    AND    ACIDS:    PROPERTIES    OF    HYDROXIDION   AND 

HYDRION. 

a.  Examine  distilled  water  in  respect  to  (a)  taste,  (6) 
behavior  with  litmus,  (c)  conductivity  (cf.  1,  6). 

b.  Dissolve  a  small  piece  of  sodium  hydroxide  in  water 
and  examine  the  solution  in  respect  to  (a)  taste,  by  diluting  a 
little  and  tasting  one  drop,  (6)  behavior  with  litmus,  (c)  con- 
ductivity (cf.  1,  d).     These  properties  belong  to  aqueous  solu- 
tions of  all  bases.     What  component  alone  is  common  to  all 
such  solutions  and  has  the  above  properties  ? 

How  can  sodium  hydroxide  be  obtained  in  solid  form, 
starting  from  sodium  and  from  sodium  oxide  respectively 
[R]  ?  Leave  a  small  piece  of  the  solid  exposed  to  the  air  for 
24  hours.  Examine  the  result  ( ?)  and  add  excess  of  hydro- 
chloric acid  ( ?).  Explain. 

c.  Examine  an  aqueous  solution  of  hydrochloric  acid  in 
respect   to  (a)  taste,  (6)  behavior    toward  litmus,  (c)  conduc- 
tivity (cf.  1,  e\  (d)  action  on  a  piece  of  marble,  (e)  action  on  an 
iron   nail   (clean  this   with   sandpaper  before  use).      These 
properties  are  shown  by  all  aqueous  solutions  of  acids.     What 
component  alone  is  common  to  all  such  solutions  and  has 
these  properties? 

How  is  the  solution  of  this  acid  made  ? 

d.  Take  the  solution  of  hydrogen  chloride  in  toluene  and 
examine  it  in  respect  to  (a)  conductivity  (cf.  1, 0),  (&)  action  on 
a  piece  of  marble,  dried  in  advance  by  heating  in  a  dry 
porcelain  dish  for  a  few  moments,  (c)  action  on  an  iron  nail 
(clean  as  before).      Be  sure  that  perfectly  dry  vessels  are 
used  in  these  experiments.  Compare  and  interpret  the  results 
in  c  and  d.     What  body  whose  presence  might  have  been 
expected  is  absent  from  this  solution  ? 

e.  Recall  the  action  of  concentrated  sulphuric  acid  on  zinc 
(p.  22,  1,  e)  and  the  action  of  dilute  sulphuric  acid  on  zinc 
(p.  22,  1,  c).     Recollect  that  the  former  is  a  poor  conductor 
and  the  latter  a  good  conductor.     To  what  inference  does  the 
last  fact  in  itself  lead?     Can  you  explain  the  two  different 
chemical  actions  by  the  help  of  this  inference?     What  body 


INTERACTIONS   OF   ACIDS,    BASES,    AND    SALTS         49 

is  acted  upon  bv  the  zinc  in  the  former  action?  To  what 
class  of  actions  does  this  belong?  What  are  the  five  compo- 
nents of  dilute  sulphuric  acid?  Which  of  them  is  affected 
by  the  zinc  and  how? 

3.  SALTS:  PHYSICAL  PROPERTIES  OF  THEIR  IONS. 

a.  Examine  a  solution  of  potassium  bromide.  What  is 
the  color  of  bromidion  ?  Take  a  minute  amount  ('say  0.2  g.) 
of  cupric  bromide  in  a  dry  test-tube.  Add  two  drops  of  water 
and  agitate  for  some  time  ( ? ).  Then  add  more  water,  a  drop 
or  two  at  a  time,  agitating  vigorously  and  giving  the  substance 
time  to  dissolve,  if  it  can,  after  each  addition.  Continue  the 
addition  of  water  cautiously  until  the  substance  has  all  dissolved 
and  afterward  until  the  change  in  color  is  complete,  and  then 
stop.  What  is  the  color  of  the  molecules  of  cupric  bromide? 
What  is  the  color  of  cuprion?  Compare  the  color  with  that 
of  cupric  sulphate  solution  (I).  Now  add  solid  potassium 
bromide  to  the  solution  and  shake  vigorously  ( ?).  Interpret 
the  result. 

6.  Make  solutions  of  chrom-alum,  cobalt  chloride,  potas- 
sium permanganate,  and  potassium  dichromate  from  the 
solids  and  dilute  to  see  whether  any  change  in  color  occurs. 
What  are  the  colors  of  trichromion.  cobaltion.  permangananion, 
and  dichromanion?  These  colors  are  useful  for  purposes  of 
recognition. 

c.  Aqueous  solutions  of  substances  of  this  kind  all  con- 
duct electricity  (c/.  1.  c). 

4.  IONIC  CHEMICAL  CHANGES  :  I.  NEUTRALIZATION.    When  di- 
lute   solutions  of  two  ionogens  are  mixed,  no  appreciable 
change  occurs,  unless  one  (or  both  I  of  the  two  new  ionogens 
which  may  be  formed  by  union  of  the  ions  crosswise  is  a  little 
ionized  substance.     In  this  latter  event  however  a  noteworthy 
chemical  change  is  encountered.      Such  chemical  changes, 
producing  soluble  products,  are  illustrated  in  4.  5,  and  6. 

Dissolve  about  10  g.  of  sodium  hydroxide  in  100  c.c.  of 
distilled  water.  Place  the  solution  in  a  burette.  Take  about 
6  c.c.  of  concentrated  hydrochloric  acid  in  an  evaporating- 
dish,  add  about  half  its  volume  of  distilled  water,  and  then 
two  drops  of  phenolphthalein  solution,  and  allow  the  alkali 
to  run  in  drop  by  drop  until  the  last  drop  confers  the  faintest 
perceptible  pink  tinge  on  the  whole  solution.  Repeat  the 
experiment,  if  you  do  not  at  first  succeed  in  stopping  at  the 
right  point.  Concentrate  the  solution  on  the  sand  bath  until 
a  drop  deposits  crystals  on  cooling,  and  then  remove  the  dish 
from  the  sand  bath  promptly  and  set  it  aside.  When  sufficient 


50  IONIC    CHEMICAL    ACTIONS 

crystals  have  appeared,  dry  them  with  filter  paper  and  exam- 
ine with  respect  to  (a)  form,  (6)  taste,  (c)  exposure  to  moist  air, 
(d)  action  of  a  solution  on  litmus,  (e)  conductivity  of  aqueous 
solution  (done  already,  1,  c).  Construct  a  table  comparing  the 
substance  in  these  respects  with  the  materials  from  which  it 
was  made.  Compare  the  substance  with  common  salt  on  the 
side-shelf.  How  would  you  determine  whether  a  substance 
obtained  in  this  way  contained  "  water  of  crystallization  "  or 
not?  Make  the  necessary  experiments  (?).  Wash  out  the 
burette. 

Name  all  the  physical  components  of  the  solutions 
of  the  acid  and  base  used  in  the  present  experiment.  In 
what  relative  proportions  are  they  present  (see  Appendix)? 
When  the  two  systems  are  mixed,  which  components  will  unite 
to  form  new  bodies,  and  to  what  extent  (see  Appendix)? 
Which  of  these  changes  will  be  the  most  extensive?  Express 
this  change  in  symbols.  What  is  the  cause  of  the  complete- 
ness of  the  action  t 

The  first  experiment  on  the  law  of  definite  proportions 
(p.  10,  2,  a)  presents  another  case  of  neutralization.  Answer 
the  same  questions  in  regard  to  this  action. 

Define  neutralization  in  terms  of  the  ionic  theory. 

5.  PARTIAL  NEUTRALIZATION:  ACID  SALTS.  Fill  one  burette 
with  potassium  hydroxide  solution.  Add  30  c.c.  of  concen- 
trated sulphuric  acid  to  70  c.c.  of  water  in  a  beaker  and  fill 
the  other  burette  with  the  cold,  diluted  acid.  Ascertain,  as  in 
4(g.  t?.),  what  volume  of  the  alkali  will  neutralize  5  c.c.  of  the 
acid,  concentrate  by  evaporating  to  about  12  c.c.,  remove  the 
dish  from  the  steam  bath,  and  allow  the  resulting  solution  to 
crystallize.  Dry  the  crystals  on  filter  paper.  To  a  second 
portion  of  the  acid,  twice  as  great  as  before  (10  c.c.),  add  exactly 
the  same  amount  of  alkali,  evaporate  to  about  5  c.c.,  and  treat 
as  before. 

Compare  the  two  lots  of  crystals  as  regards  (a)  form,  (6) 
taste,  (c)  reaction  of  solution  with  litmus,  (d) "  water  of  crystal- 
lization." Confirm  by  examining  specimens  of  the  same  sub- 
stances from  the  side-shelf.  Wash  the  burettes  very  carefully 
to  prevent  the  stopcocks  becoming  fast. 

Name  all  the  things  (five  of  them)  which  the  mixture 
known  as  a  solution  of  potassium  hydroxide  contains :  also  all 
the  things  (five  of  them)  which  the  mixture  known  as  dilute 
sulphuric  acid  contains.  Describe  what  happens  to  each  of 
these,  so  far  as  they  are  changed  in  the  course  of  the  titration, 
expressing  the  changes  in  equations.  If  the  solution  had 
been  one  of  ammonium  hydroxide,  what  additional  kind  of 
material  would  have  been  present  and  what  changes  would  it 


INTERACTIONS    OF    ACIDS,    BASES,    AND    SALTS         51 

have  undergone  in  the  course  of  the  neutralization?  Express 
these  changes  also  in  equations. 

[Advanced  students.]  Make  a  solution  of  sodium  bicar- 
bonate and  test  it  with  litmus  (?).  Why  do  some  acid  salts 
show  no  acid  reaction  with  litmus  ?  Define  the  terms  "  normal 
salt "  and  "  acid  salt."  Test  cupric  sulphate  and  ferric  chloride 
solutions  with  litmus  ( ?).  Why  are  some  normal  salts  basic 
and  others  acid  in  their  reactions  toward  litmus?  Answer 
these  questions  in  terms  of  the  ionic  theory. 

What  is  meant  by  the  term  "  basic  salt  ?  "  Give  exam- 
ples [R]. 

Note.  —  Aqueous  solutions  of  suitable  concentration  of  the 
substances  used  in  all  experiments  will  be  found  on  the  side- 
shelf.  These  should  be  used,  excepting  where  the  making  of  a 
solution  is  expressly  directed.  Examine  the  same  substance  in 
the  solid  form  when  you  fetch  the  solution. 

6.  IONIC  CHEMICAL  CHANGES  :  II.  FORMATION  OF  "  WEAK  " 
BASES  AND  ACIDS. 

a.  Formation  of    an  hydroxide.      To   some  ammonium 
chloride  solution  in  a  test-tube  add  some  sodium  hydroxide 
solution  ( ?).     Observe  the  odor. 

Name  all  the  physical  components  of  each  solution  and 
the  relative  proportions  in  which  they  are  present  (see  Appen- 
dix). When  the  two  solutions  are  mixed,  which  components 
will  unite  and  form  new  bodies,  and  to  what  extent  (see 
Appendix)  ?  Which  of  these  changes  will  be  the  most  exten- 
sive? Express  this  change  in  symbols. 

Formulate  also  the  process  by  which,  here,  ammonia  is  set 
free.  Define  the  term  "  weak  base  "  and  illustrate. 

This  kind  of  action  is  often  accompanied  by  precipitation, 
as  in  making  zinc  hydroxide.  This  is  formulated  as  follows: 

Zn  +  2OH  ^  Zn(OH) 2 (dissolved)  ±5  Zn(OH)2  (solid). 

On  what  two  things  does  the  completeness  of  such  an 
action  depend?  Which  exercises  here  the  decisive  influ- 
ence [R]? 

b.  Formation  of  an  acid.     Add  a  few  drops  of  concen- 
trated sulphuric  acid  to  a  concentrated  solution  of  sodium 
acetate    in   a   test-tube   and,  if    necessary,  warm  gently  (?). 
Observe  the  odor. 

Answer  the  same  questions  as  in  the  second  paragraph 
of  a. 

Define  the  term  "  weak  acid  "  and  illustrate. 

Give  a  list  of  acids  which  might  be  formed  by  union  of 
the  proper  ions  after  the  manner  of  acetic  acid  (see  Ap- 
pendix). 


52  IONIC    CHEMICAL    ACTIONS 

This  kind  of  action  is  often  accompanied  by  precipitation 
as  in  making  silicic  and  boric  acids  [R].  Formulate  the  action 
producing  metasilicic  acid  from  sodium  metasilicate  on  the 
model  given  above.  Which  is  here  probably  the  chief  cause 
of  the  completeness  of  the  action? 

7.    IONIC     CHEMICAL     CHANGES!       III.    FORMATION     OF    SALTS. 

With  a  few  exceptions  (illustrations?  See  Appendix),  salts 
are  all  extensively  ionized  in  dilute  solutions.  Decided  chem- 
ical changes  therefore  are  not  produced  by  mixing  their  ions 
in  solution.  When,  however,  the  molecules  are  sparingly 
soluble  in  water,  precipitation  occurs  and  almost  complete 
chemical  change  may,  nevertheless,  take  place.  The  following 
experiments  deal  with  changes  which  occur  on  this  account : 

a.  Take  some  of  the  ordinary  calcium  chloride  solution  in 
one  test-tube.  Dilute  one  drop  of  it  with  a  large  amount  of 
water  in  another.  Add  a  drop  or  two  of  dilute  sulphuric  acid 
to  each  (?).  Explain. 

6.  Formation  of  salts.  Place  3  or  4  c.c.  of  silver  nitrate 
solution  in  a  test-tube  and  dilute  with  water.  Add  potassium 
chloride  solution  cautiously,  and  agitate  continuously,  until 
no  further  precipitation  occurs.  Filter,  concentrate  the  filtrate 
and  pour  it  into  a  watch  glass  to  crystallize.  Two  salts  are 
formed.  Make  lists  of  the  physical  components  of  each  solu- 
tion. Write  the  general  equation  and  also  the  two  equations 
representing  the  formation  of  the  salts  separately  from  their 
components,  and  state  when  the  formation  of  each  mainly 
occurs.  Is  the  formation  of  a  precipitate  theoretically  essen- 
tial in  order  that  any  change  may  take  place  between  salts  ? 

c.  Take  3  or  4  c.c.  of  silver  nitrate  solution,  dilute  with 
water,  and  use  one-fourth  for  each  of  the  following  ex- 
periments. 

Add  the  first  and  second  portions  of  the  silver  nitrate 
solution  to  solutions  of  calcium  chloride  and  cobalt  chloride 
respectively  ( ?).  What  do  these  results  show  the  solutions  of 
these  chlorides  and  potassium  chloride  to  possess  in  common? 

Add  the  third  portion  of  the  silver  nitrate  solution  to  a 
few  drops  of  potassium  chlorate  solution  ( ?).  What  conclusion 
may  we  draw  from  this  result  in  regard  to  the  ions  present  in 
the  solution  of  potassium  chlorate? 

Chloroform  and  chloracetic  acid  fail  to  give  a  precipitate 
with  silver  nitrate.  How  do  these  substances  differ  from 
chlorides? 

Dilute  a  few  drops  of  silver  sulphate  solution  with  water 
and  add  some  potassium  chloride  solution  (?).  What  does 
this  show  to  be  common  to  the  solutions  of  silver  nitrate  and 
sulphate? 


INTERACTIONS    OF    AC'IDS,    BASES,    AND    SALTS         53 

To  the  fourth  portion  of  the  silver  nitrate  solution  add 
potassium  cyanide  solution  [Care  !  Poison  !]  until  the  precipi- 
tate at  first  formed  is  re-dissolved  (see  note).  Now  add  a  drop 
or  two  of  potassium  chloride  solution  ( ?).  What  is  absent 
from  this  silver  solution  and  present  in  those  of  silver  nitrate 
and  sulphate  as  judged  by  the  potassium  chloride  test  ? 

Note.  —  The  solubility  of  an  "insoluble"  substance  is  not 
usually  affected  by  the  mere  physical  presence  of  another  soluble 
substance,  whether  this  be  a  new  reagent  or  an  excess  of  an  old 
one.  The  only  body  playing  the  part  of  a  solvent  in  such  cases 
is  water.  When  solution  occurs  the  acid  or  other  chemical  rea- 
gent simply  transforms  by  chemical  change  a  precipitated  material 
into  a  new  substance  soluble  in  water  and  has  itself  no  share  in 
promoting  the  physical  process  of  solution.  Here  the  new  body 
is  potassium  argenticyanide,  KAg(CN)3.  What  do  the  ions  of 
this  substance  appear  to  be? 

d.  Place  in  three  test-tubes  small  quantities  of  solutions 
of  sodium  sulphide,  sodium  sulphate,  and  sodium  thiosul- 
phate,  dilute  each  with  water,  and  add  to  each  a  few  drops  of 
cadmium  nitrate  solution  (?).     Assuming  that  we  know  the 
nature  of  the  precipitate  in  the  first  case  and  the  ions  in  that 
case,  what  conclusion  do  we  draw  from  the  behavior  of  the 
other  two  solutions  ? 

e.  In  what  way  does  the  lecture  experiment  with  potas- 
sium ethyl  sulphate  and  barium  chloride  illustrate  the  same 
points  ? 

/.  Put  some  highly  diluted  potassium  permanganate 
solution  in  one  test-tube  and  some  diluted  manganous  chloride 
solution  in  another.  Add  to  each  a  few  drops  of  sodium  car- 
bonate solution  (?).  Why  does  the  second  behave  differently 
from  the  first  ? 

g.  Place  approximately  equal  small  quantities  of  sodium 
hydrogen  carbonate  (bicarbonate)  and  potassium  hydrogen  tar- 
trate  in  a  mortar  and  rub  them  together  ( ?).  Now  throw  this 
mixture  into  a  small  beaker  of  water?  The  gas  is  carbon  diox- 
ide and  comes  from  the  spontaneous  decomposition  of  the 
molecules  of  one  of  the  products  of  the  interaction.  Test  the 
solution  for  hydrion  (?,  test?). 

To  explain  this  action  we  must  know  the  ions  of  the  in- 
gredients. Kalion  and  natrion  may  safely  be  assumed.  Make 
separate  solutions  of  the  ingredients  and  test  each  for  hydrion. 
Make  lists  of  the  physical  components  of  each  solution  so  far 
as  these  data  enable  you  to  do  so.  Which  of  these  compo- 
nents will  unite  to  form  a  new  body  (see  Appendix)? 

Formulate  the  action  by  which  this  body  is  formed  and 
complete  the  explanation. 


54  IONIC    CHEMICAL    ACTIONS 

8.  IONIC  CHEMICAL  CHANGES:  IV.  DISPLACEMENT  OF  ONE  ION. 

a.  Place  several  pieces  of  granulated  zinc  in  a  dilute 
solution  of  cupric   sulphate   and   set   aside  till  the  change 
is  complete   (?).      Stirring  will   hasten   the  chazige  (why?). 
Filter  and  examine  the  precipitate  and  filtrate  ( ?)  in  turn  as 
follows: 

Treat  the  precipitate  with  a  drop  or  two  of  concentrated 
nitric  acid  in  a  test-tube  (?),  and  add  ammonium  hydroxide  to 
the  result  ( ?).  Treat  a  fragment  of  copper  turnings  in  the 
same  way  ( ?). 

Add  colorless  ammonium  sulphide  solution  to  the  solu- 
tion ( ?).  What  does  it  contain  [R]  ? 

b.  In  what  way  do^the  experiments  in  Chap.  VI,  1  (p.  22) 
illustrate  this  kind  of  "action?     Answer  the  same  question  in 
regard  to  Chap.  VI.  2,  a,  and  d  (p.  23). 

How  does  the  action  in  Chap.  VI,  1,  e  differ  from  these  and 
the  present  experiment?  Which  physical  components  were 
active  in  1,  e? 

c.  The  order  in  which  the  metals  stand  in  reference  to 
their  tendency  to  enter  the  ionic  condition  from  the  metallic 
(the  order  of  decreasing  "  solution  tension,"  known  also  as  the 
"electro-motive  series")  is  as  follows: 

Alkali  metals  [R].  Iron  (Antimony). 

Alkaline  earth  metals  [R].     Cobalt.  (Bismuth). 

Magnesium.  Nickel.  Mercury. 

Aluminium.  Tin.  Silver. 

Manganese.  Lead.  Palladium. 

Zinc.  Hydrogen.      Platinum. 

Chromium.  (Arsenic).        Gold. 

Cadmium.  Copper. 

Each  of  these  metals  will  in  general  displace  from  a  nor- 
mal solution  the  ions  of  any  metal  below  it  in  the  series  [R. 
Electro-Chemistry].  The  places  of  the  metals  in  parentheses 
are  only  approximate. 

d.  Examine  your  notes  on  Chap.  X,  4  and  5  (pp.  40-41). 
What  is  the  action  of  free  chlorine  on  bromide  ions  (4,  a)  ? 
What  is  the  action  of  free  chlorine  on  iodine  ions  (4,  6)? 
What  is  the  action  of  free  bromine  on  iodine  ions  (4,  c)? 
What  is  the  action  of  free  bromine  on  sulphur  ions  (5,  a)? 
What  is  the  action  of  free  iodine  on  sulphur  ions  (5,  6)? 
Arrange  these  four  elements  in  a  series  similar  to  that  for 

metals  given  above.  Where  would  you  place  fluorine  in  this 
series  ?  Can  you  indicate  the  approximate  position  of  oxygen 
(5,  b,  last  par.)? 


INTERACTIONS   OF    ACIDS,    BASES,    AND   SALTS         55 

9.  What  three  distinct  kinds  of  chemical  change  involv- 
ing ions  are  illustrated  in  this  chapter  (c/.  1,  4,  5,  6,  7,  8)? 
Give  examples  of  each.     A  fourth  kind  occurred  in  Chap.  XI, 
3  (p.  43),  and  again  in  5,  b  (p.  45),  and  still  again  in  7,  b  (p.  45). 
What  was  this   kind?     The  fifth  kind  will  be  met  with  in 
Chap.  XIII,  3,  e  (p.  58),  and  in  Chap.  XV,  4,  c  (p.  69). 

10.  In  previous  lecture  and  laboratory  experiments  we 
have  observed  the  formation  of  acids,  bases,  and  salts  in  other 
ways  than  those  illustrated  in  this  chapter.     These  ways  are 
non-ionic,  or  not  distinctly  ionic.     Give  illustrations  of  such 
of  these  ways  as  you  recall:  acids,  two  ways;  bases,  two  ways; 
salts,  three  ways.    Two  other  ways  of  making  salts  will  occur 
later. 


CHAPTER  XIII. 

SULPHUR  AND  ITS  COMPOUNDS. 

1.  SULPHUR. 

a.  Place  a  few  grams  of  sulphur  in  a  dry  test -tube  and 
heat   slowly  with   a  small   flame   until  the   substance  boils. 
Describe  all  the  changes  which  occur. 

b.  Pour  the  boiling  /sulphur  into  a  beaker  of  cold  water 
and  examine  the  product.     How  could  you  discover  whether 
the  change  was  due  to  chemical  action  on  the  water  or  not? 
Set  the  product  aside  and  examine  it  after  a  day  or  two  ( ?). 

In  what  substance  have  you  found  roll  sulphur  soluble  ? 
Find  out  whether  this  specimen  is  completely  soluble  in  the 
same  substance. 

c.  Rub  a  pinch  of  sulphur  with  a  globule  of  mercury 
[Store-room]  in  a  mortar  ( ?).    Recall  cases  of  the  union  of 
sulphur  with  metals  which  you  have  met  previously. 

d.  Make  a  thin  paste  of  flowers  of  sulphur  and  distilled 
water  by  rubbing  them  together  in  a  mortar,  spread  it  evenly 
over  the  inside  of  a  carefully  cleaned,  narrow -mouthed  bottle. 
Allow  the  bottle  to  stand  in  your  desk  for  several  days.    If  the 
sulphur  dries,  repeat  the  moistening  as  often  as  is  necessary. 
Examine  the  mass.    Notice  its  odor  ( ?)  and  hold  a  rod  dipped 
in  ammonium  hydroxide  solution  over  it  (?).     If  it  has  dried 
up  again,  mix  with  2-3  c.c.  of  water.     Then  filter,  using  a  very 
small  filter  paper,  and  test  the  filtrate  with  neutral   litmus 
paper  (?)  and  with  barium  chloride  solution  (?).     The  result 
of  the  latter  test  may  be  slow  in  appearing. 

e.  [Hood.]     Place  a  few  particles  of  sulphur  on  the  in- 
verted lid  of  a  porcelain  crucible  and  heat  strongly  ( ?).   Notice 
the  odor  of  the  gas  and  apply  the  ammonia  test  (?)   Contrast 
the  results  of  d  and  e,  —  the  effects  of  oxidizing  sulphur  in 
presence  and  in  absence  of  water. 

2.  HYDROGEN  SULPHIDE  [Hood]. 

a.  Place  a  little  ferrous  sulphide  in  a  test-tube.  Add 
some  water  for  the  purpose  of  dilution  and  then  concentrated 
hydrochloric  acid  until  a  moderately  rapid  evolution  of  gas 
ensues  (?).  Notice  the  odor  of  the  gas.  Explain  this  action 

56 


SULPHUR    AND    ITS    COMPOUNDS  57 

with  the  help  of  the  ionic  theory,  noting  the  extent  to  which 
hydrogen  sulphide  is  ionized  (Appendix). 

Use  a  Kipp's  apparatus  and  wash  bottle  containing  water 
for  obtaining  the  gas  required  in  2,  fr,  3,  and  4. 

b.  When  the  air  has  been  displaced,  attach  a  nozzle  and 
set  fire  to  the  gas.    What  are  the  products  of  its  combustion? 

Hold  a  porcelain  dish  in  the  flame  ( ?).  What  substance  is 
shown  by  this  observation  to  exist  free  in  the  interior  of  the 
flame?  What  other  free  body  do  you  infer  must  be  present  in 
the  same  region?  From  these  facts  you  may  infer  that  the 
action  takes  place  in  two  stages  (?).  What  light  do  these  facts 
throw  on  the  difficulty  in  making  the  compound  by  direct 
union  of  the  elements  ? 

c.  For  comparison  with  2,  a,  treat  two  portions  of  powdered 
[Iron  mortar]  ferrous   sulphide  in  separate  test-tubes,   one 
with  concentrated   sulphuric  acid  in  the  cold  ( ?)  and  then 
in  the  heat  ( ?),  the  other  with  dilute  sulphuric  acid  ( ?). 

What  physical  component  is  present  in  large  amount  in 
the  concentrated  acid,  while  in  dilute  sulphuric  acid  it  is 
almost  wanting?  Can  you  explain  the  difference  in  the  result 
on  this  ground  (c/.  p.  54,  8,  6)? 

3.  PROPERTIES  OF  HYDROGEN  SULPHIDE:  I  [Hood]. 

a.  Prepare  an  aqueous  solution  of  the  gas  in  a  carefully 
cleaned  test-tube,  and  expose  the  greater  part  of  it  to  the  air 
for  some  time  in  an  open  narrow-mouthed  bottle  ( ?).    Pre- 
serve the  rest  for  use  in  4,  g. 

Place  the  following  substances  in  test-tubes  and  pass  a 
vigorous  stream  of  the  gas  through  each  for  a  few  moments. 
This  gives  the  same  result  as  adding  an  aqueous  solution  of 
the  gas.  Study  each  action  carefully.  In  explaining  the 
actions  in  3,  c,  d,  and  e  and  in  4,  remember  that  hydrogen 
sulphide  is  somewhat  ionized  and  that  some  sulphides  give 
even  less  sulphidion  under  these  conditions  than  it  does. 

b.  Concentrated    sulphuric    acid  (?).      What    substance 
might  be  used  for  drying  the  gas,  and  which  substances  com- 
monly used  for  drying  would  be  unsuitable? 

c.  Acidified  potassium  dichromate  solution  (?).    ["Acidi- 
fied "  generally  means  that  a  dilute  acid  has  been  added  until 
the  solution  has  an  acid  reaction  toward  litmus.     Use  here  a 
considerable  excess  of  sulphuric  or  hydrochloric  acid,  and  do 
not  forget  that  excess  of  the  acid  is  present.]    Two  kinds  of 
ionic  change  occur  here  (c/.,  p.  55,  9). 

d.  Diluted  and  acidified  potassium  permanganate  solu- 
tion (?). 


58          SULPHUR  AND  ITS  COMPOUNDS 

e.  Ferric  chloride  solution  ( ?).  Saturate  (test  ?)  the  solu- 
tion with  the  gas.  Filter  and  add  potassium  ferricyanide 
solution  to  the  filtrate  ( ?). 

The  significance  of  the  result  will  be  brought  out  by 
taking  ferric  chloride  and  ferrous  sulphate  solutions  in 
separate  test-tubes  and  adding  the  ferricyanide  to  each  ( ?). 
Formulate  these  two  actions  ionically. 

Can  you  now  state  what  the  action  of  hydrogen  sulphide 
was?  How,  precisely,  were  the  ions  of  iron  changed  (cf.  p. 
55,  9)? 

Recall  the  action  of  hydrogen  sulphide  solution  on 
iodine  (p.  40,  5,  &).  What  general  property  of  hydrogen  sul- 
phide do  these  experiments  illustrate? 

4.  PROPERTIES  OF  HYDROGEN  SULPHIDE:  II.  SULPHIDES  OF 
METALS  [Hood].  Dilute  a  few  drops  of  each  of  the  following 
solutions  with  five  to  ten  times  their  volume  of  water,  pass 
hydrogen  sulphide  to  saturation  (test  ?)  into  each,  and  note  the 
results  (cf.  3,  a,  second  par.): 

a.  Cupric  sulphate. 

b.  Cadmium  sulphate. 

c.  Lead  acetate. 

d.  Zinc  acetate. 

e.  Barium  chloride. 

All  these  actions  are  reversible  when  a  sufficient  concentra- 
tion of  acid  (i.  e.,  hydrion)  is  present  in  excess.  In  chemical 
analysis  those  of  the  above  actions  which  are  reversed  by  a 
rather  small  concentration  of  acid  (i.e.,  dilute  acid),  and  those 
of  them  which  require  a  high  concentration,  are  put  into  two 
separate  classes.  There  are  also  sulphides  which  are  almost 
completely  decomposed  (and,  in  any  case,  completely  dis- 
solved) by  a  mere  equivalent  of  acid. 

Add  pure  dilute  hydrochloric  acid  to  the  contents  of  each 
of  the  above  test-tubes,  agitate,  and  observe  the  effect. 
Classify  these  metals  according  as  their  sulphides  seem  to 
belong  to  one  or  other  of  these  three  classes. 

[Advanced  students.]  Give  the  explanation  of  these  facts 
in  accordance  with  the  theory  of  ionization. 

/.  Add  sodium  carbonate  solution  to  lead  nitrate  solution 
in  a  test-tube,  filter,  and  expose  the  paper  with  its  precipitate 
to  hydrogen  sulphide  gas  ( ?). 

g.  Test  the  rest  of  the  aqueous  solution  of  hydrogen  sul- 
phide from  3,  a  with  litmus  pap  er  ( ?). 

h.  Pass  a  stream  of  the  gas  into  a  few  c.c.  of  sodium 


SULPHUR  AND  ITS  COMPOUNDS 


59 


hydroxide  solution  in  a  test-tube  until  the  solution  is  perfectly 
saturated  (test  ?)  ( ?).  Test  the  solution  with  litmus  paper 
and  divide  into  three  parts. 

To  the  first  add  dilute  hydrochloric  acid  ( ?). 

To  the  second  add  a  little  powdered  roll  sulphur  and  shake 
from  time  to  time  ( ?).  After  half  an  hour,  or  when  the  solu- 
tion has  become  very  yellow  in  color,  filter,  and  acidify  the 
filtrate  with  dilute  hydrochloric  acid  (?).  What  did  the  yel- 
low solution  contain  [R]  ?  Recall  an  experiment  with  iodine 


Fig.  18. 


whi3n  resembles  this  action  of  sulphur  on  sodium  sulphide. 
Filter,  wash  the  precipitate  with  water,  dry  it,  and  test  its 
solubility  in  carbon  disulphide  and  its  combustibility. 

Leave  the  third  portion  in  a  partially  closed  bottle  for  sev- 
eral days(?).  After  a  change  in  its  appearance  is  plainly 
perceptible  add  dilute  hydrochloric  acid  in  excess  ( ?).  Explain. 

5.  SULPHURIC  ACID  [Two  students  working  together]. 

a.  Obtain  a  distilling  flask,  a  safety  bottle  with  rubber 
connections,  a  rather  wide-mouthed  1 -liter  bottle,  and  a  Chap- 
man pump  from  the  store-room  [Temp,  order].  Fit  the  large 
bottle  as  in  Fig.  18.  Charge  the  hard  glass  tube  with  about 
10  g.  of  granular  pyrite.  Place  in  the  distilling  flask  about 
lOc.c.  of  pure  concentrated  nitric  acid  [Side-shelf].  The 
safety  bottle,  half  filled  with  water  to  show  the  rate  at  which 
air  is  being  drawn  through  the  apparatus,  is  attached  to  the 
water  pump.  The  total  air  admitted  is  regulated  by  the 
screw  clamp  near  the  pump,  while  the  proportions,  which  pass 
over  the  pyrite  and  carry  over  the  nitric  acid  vapor  respect- 


60  SULPHUR    AND    ITS    COMPOUNDS 

ively  are  regulated  by  pinching  one  of  the  tubes  with  the 
finger  and  thumb. 

First  heat  the  pyrite  in  a  very  gentle  stream  of  air  until 
the  sulphur  burns.  Then  warm  the  nitric  acid  and  divert 
part  of  the  air  current  so  that  it  may  carry  over  a  little  of  the 
vapor  of  the  acid  ;  heat  the  pyrite  strongly  and  continuously. 
Repeat  the  introduction  of  air  laden  with  nitric  acid  at  inter- 
vals, by  pinching  the  tube  admitting  air  to  the  pyrite-burner, 
whenever  the  disappearance  of  the  red  fumes  in  the  bottle 
shows  that  a  further  supply  is  needed. 

After  a  crust  of  crystals  ( ?)  has  formed  in  the  bottle  (there 
may  be  considerable  delay  before  crystallization  starts)  remove 
the  attachments  and  blow  the  gases  from  the  interior  by 
means  of  the  bellows.  If  crystallization  fails  to  begin  after  a 
reasonable  time  (note  that  an  interaction  even  between  the 
molecules  of  gases  may  be  slow,  in  spite  of  the  completeness 
of  the  mixing),  the  cause  is  either  the  introduction  of  too 
much  water  along  with  the  nitric  acid,  or  the  high  tempera- 
ture produced  by  chemical  actions  taking  place  in  the  bottle. 
Removing  the  attachments  and  cooling  the  bottle  in  a  stream 
of  water  frequently  brings  it  about. 

Add  4-5  c.c.  of  water  and  wash  down  the  crystals  with  it. 
Describe  all  that  happens.  If  more  of  the  product  is  required, 
the  apparatus  may  be  connected  up  again  and  a  further  sup- 
ply of  sulphur  dioxide  drawn  into  the  bottle  and  subsequently 
more  nitric  acid  vapor  can  be  added.  Finally  any  remaining 
crystals  may  be  decomposed  by  water. 

Filter  the  liquid  in  the  bottle  through  a  very  small  filter 
paper  into  a  dish,  rinsing  the  bottle  with  2-3  c.c.  of  water, 
and  evaporate  on  the  sand  bath  [Hood]  until  the  liquid  begins 
to  fume  strongly  ( ?).  This  will  remove  any  nitric  or  nitrous 
acid  that  it  may  contain.  Use  the  result  for  b. 

b.  Dilute  the  product  from  a  by  adding  it  to  2-3  volumes 
of  water.     Test  the  solution  with  litmus  paper  (?).     In  one- 
third  of  it  place  a  piece  of  zinc  or  iron  ( ?).     To  a  small  part 
add  barium  chloride  solution  (?).     With  the  remainder  make 
marks  on  a  piece  of  paper  by  means  of  a  match  dipped  in  the 
liquid.     Put  the  match  and  the  paper  on  a  radiator  to  dry  ( ?). 

c.  [Hood.]  Take  2-3  c.c.  of  concentrated  sulphuric  acid  in 
a  test-tube.    Suspend  a  thermometer  so  that  the  bulb  is  com- 
pletely immersed  in  the  acid.     Heat  the  contents  of  the  tube 
by  means  of  a  small  flame  and  note  the  temperature  at  which 
any  effect  (?)  is  observed  and  that  at  which  it  is  conspicuous. 
[CAUTION:     During  the  heating  remember  that,  if  the  tube 
should  crack,  the  hot  acid  may  splash  on  the  clothes  and 


SULPHUR    AND    ITS    COMPOUNDS  61 

hands  and  produce  severe  burns.     Exercise  proper  caution. 
Be  careful  not  to  wash  out  this  tube  until  the  acid  has  cooled.] 

6.  SULPHATES.    Place  some  ferric  sulphate  in  a  hard  glass 
tube,  or  porcelain  crucible,  and  heat  strongly  with  the  blast- 
lamp,  continuing  the  heating  after  all   the  water  has  been 
driven  off  [R]  (?).    Relate  this  result  to  that  in  5,  c.     Recall 
action  of  heat  on  dehydrated  gypsum  (p.  26,  3,  d).    Classify 
sulphates  in  accordance  with  this  distinction  [R]. 

7.  SULPHUR  DIOXIDE. 

a.  Heat  a  piece  of  sulphur  and  a  piece  of  charcoal  with 
concentrated  sulphuric  acid  in  separate  test-tubes.     Notice 
the  odor  of  the  vapor.    What  property  of  sulphuric  acid  pre- 
vails in  this  case?    Recall  p.  57,  2,  c,  and  3,  &,  p.  37,  2,  a, 
and  p.  22  1,  e,  and  compare. 

Give  a  list  of  the  propsrties  of  sulphuric  acid  which  have 
been  illustrated  in  5,  b  and  c,  and  7. 

b.  [Hood.]    Prepare  a  flask  fitted  like  that  in  Fig.  10  and 
two  gas  washing  bottles  like  the  one  in  Fig.  12.    If  8  is  omitted, 
the  second  bottle  containing  the  drying  agent  (see  below)  will 
not  be  required.     Twist  up  some  copper  turnings  [Be  careful 
not  to  cut  the  fingers]  into  bunches,  place  them  in  the  flask, 
and  add  10-15  c.c.  of  concentrated  sulphuric  acid.     Attach 
the  first  of  the  two  wash  bottles  in  reversed  position,  with  the 
short  tube  next  the  flask  and  leave  it  empty  to  act  as  a  safety 
bottle  ( ?).    Put  an  inch  or  so  of  concentrated  sulphuric  acid 
in  the  second.    See  that  the  apparatus  is  air-tight. 

Heat  the  flask  and  contents  by  means  of  a  sand  bath. 
Leave  the  cork  out  at  first  and  suspend  in  the  acid  a  ther- 
mometer. Note  the  temperatures  at  which  chemical  action 
becomes  perceptible  ( ?)  and  at  which  it  is  conspicuous  ( ?). 
Relate  this  result  to  the  temperature  found  in  5,  c.  Why  can- 
not dilute  sulphuric  acid  be  used?  Connect  the  apparatus 
and  continue  heating  to  obtain  the  gas  needed  in  8  and  9. 

Note  the  appearance  of  the  contents  of  the  flask  as  the 
action  progresses,  and  account  for  it  (?).  In  this  connection 
read  9,  /. 

8.  WEIGHT  OF  A  LITER  OF  SULPHUR  DIOXIDE  [Quant.  Hood]. 
Clean  and  dry  a  250  c.c.  flask  and  provide  it  with  a  tightly 
fitting   cork.     Weigh   the  flask   and  cork.    This   gives   the 
weight  of  the  flask  filled  with  air.     Now  fill  it  completely 
with  sulphur  dioxide,  by  downward  displacement  of  air,  cork 
and  weigh  again.     To  insure  its  being  full,  repeat  this  opera- 
tion till  no  increase  in  weight  occurs.     Finally,  allow  the  gas 
to  escape,  and  determine  its  volume  by  filling  the  flask  with 


62          SULPHUR  AND  ITS  COMPOUNDS 

water  up  to  the  cork  and  weighing  again.  Observe  the  tem- 
perature and  pressure  of  the  atmosphere. 

To  obtain  the  weight  of  the  empty  flask  and  its  cork,  sub- 
tract from  the  weight  of  the  vessel  filled  with  air  the  weight, 
under  the  observed  conditions,  of  a  volume  of  air  equal  to  its 
content  (1  liter  pure  dry  air  weighs  1.293  g.  under  normal  con- 
ditions). 

The  difference  between  this  corrected  weight  and  that  of 
the  flask  filled  with  sulphur  dioxide  is  the  weight  of  the  latter. 
Reduce  the  volume  of  the  gas  to  normal  conditions  and  calcu- 
late the  weight  of  1  liter  (?)  and  of  22.39  liters  (?). 

Enumerate  carefully  all  the  sources  of  error  to  which  you 
would  expect  this  way  of  determining  the  density  of  a  gas  to 
be  liable.  In  doing  this,  consider  each  detail  of  the  operation 
very  critically. 

9.  SULPHUROUS  ACID  [Hood]. 

a.  Pass  the  gas,  prepared  as  in  7,  ft,  for  a  few  minutes 
into  a  test-tube  full  of  water  ( !).     Test  the  solution  with  lit- 
mus paper  [R]  ( ?).     The  result  shows  what  is  present  in  the 
aqueous  solution  of  the  gas.    This  product  is  to  be  regarded 
as  the  active  substance  in  the  following  paragraphs. 

b.  To  one-half  of  the  liquid  add  barium  chloride  solution 
(?)and  excess  of  pure  hydrochloric  acid(?).     Is  the  action 
of  barium  chloride  on  the  substance  recognized  in  a  reversible 
or  not? 

Then  add  bromine  water  to  the  same  portion  ( ?).  What 
is  the  precipitate  [R]  (?)  and  how  was  it  formed? 

c.  Expose  the  rest  of  the  solution  to  the  air  in  a  beaker 
for  a  day  or  two,  testing  a  few  drops  with  pure  hydrochloric 
acid  and  barium  chloride  solution  from  time  to  time  (?).    Re- 
late the  result  to  those  in  1,  d  and  e  and  9,  b. 

d.  Pass  a  stream  of  gas  into  test-tubes  containing  solutions 
of  potassium  dichromate  ( ?)  and  potassium  permanganate  ( ?), 
each  acidified  (cf.  p.  57,  3,  c),  with  dilute  sulphuric  acid,  until 
no  further  change  is  observed  [R]. 

e.  Collect  a  bottleful  of  the  gas  by  downward  displace- 
ment of  air  and  put  in  it  some  moist  litmus  paper  and  some 
grass  (?). 

/.  Allow  the  flask  in  which  the  sulphur  dioxide  was  pre- 
pared to  remain  over  night,  examine  and  describe  the  appear- 
ance of  all  its  contents  carefully.  Then,  if  there  is  any  solid 
matter  in  the  bottom,  pour  awTay  the  liquid  and,  after  renewed, 
minute  examination  of  the  solid,  throw  some  of  the  latter  into 
a  beaker  of  water.  (If  there  is  no  solid,  pour  part  of  the 


SULPHUR    AND    ITS    COMPOUNDS  63 

liquid  into  a  large  amount  of  water.)  What  are  the  physical 
properties  of  the  solid?  What  do  you  observe  when  it  dis- 
solves in  water?  Explain. 

10.  SULPHITES. 

a.  Add  any  dilute  mineral  acid  to  sodium  sulphite  or 
sodium  bisulphite  (?). 

b.  Heat  strongly  [Blast-lamp]  about  a  gram  of  each  of 
these  salts  separately  in  dry  test-tubes  until  no  further  change 
is  observed  ( ?).     In  each  case  begin  to  heat  cautiously  and 
hold  the  tube  in  a  horizontal  position  to  prevent  cracking  by 
condensed  moisture. 

Add  dilute  hydrochloric  acid  to  each  result  (?).  If  free 
sulphur  is  observed,  account  for  its  formation. 

11.  THIOSULPHATES. 

a.  How  are  these  salts  prepared  [R]?  Take  some  diluted 
sodium  thiosulphate  solution  and  add  any  dilute  mineral  acid. 
What  appears  after  a  time  ?  Note  the  odor. 

Heat  strongly  a  small  quantity  of  sodium  thiosulphate  in 
a  dry  test-tube,  using  the  same  precautions  as  in  10,  b,  until 
no  further  change  is  observed.  Observe  the  effect  and  notice 
the  odor.  Add  dilute  hydrochloric  acid  to  the  result  ( ?). 

12.  REDUCTION  OF  SULPHUR  COMPOUNDS.     Mix  a  pinch  of 
any  salt  of  a  sulphur  acid  with  an  equal  amount  of  anhydrous 
sodium  carbonate.     Slightly  char  the  end  of  a  match  and  rub 
the  charred  part,  which  should  be  about  an  inch  in  length, 
with  a  heated  crystal  of  sodium  carbonate  [Instructions]. 
Moisten  the  above  mixture  with  water,  place  some  of  it  on  the 
end  of  the  match,  and  heat  in  the  reducing  region  of  a  small 
Bunsen  name.    Put  the  result  on  a  clean  silver  coin  lying  in 
a  watch  glass  and  moisten  with  one  drop  of  water  ( ?).    Then 
add  some  dilute  mineral  acid  and  notice  the  odor  ( ?).    This 
is  a  test  for  sulphur  in  any  form  of  combination. 


CHAPTER  XIV. 

THE   ACTIVITY    OF   ACIDS    MEASURED   CHEMICALLY. 

1.  ESTIMATION  OF  THE  RELATIVE  ACTIVITY  OF  ACIDS.  The 
relative  "  strength  "  or  activity  of  acids  (or  bases)  can  only  be 
measured  when  the  conditions  for  the  acids  compared  are  the 
same.  When  the  acids  are  not  on  the  same  footing,  as  in  the 
action  of  sulphuric  acid  on  common  salt,  giving  hydrochloric 
acid  in  the  absence  of  much  water  (p.  32,  3,  d),  the  fact  that  the 
volatile  acid  is  almost  entirely  displaced  does  not  give  any 
information  about  the  relative  "  strength  "  of  the  two  acids. 
The  following  experiment  illustrates  the  simplest  of  the  four 
or  five  methods  of  comparing  the  activity  of  acids. 

a.  When  methyl  acetate  is  mixed  with  water,  it  undergoes 
hydrolysis  very  slowly,  acetic  acid  and  methyl  alcohol  being 
formed:  CH3.C2H3O2+H2O  ±5  CH3OH+HC2H3O2.  Add 
about  1  c.c.  of  methyl  acetate  to  10  c.c.  of  distilled  water  in  a 
test-tube,  test  with  neutral  litmus  paper  ( ?),  and  cork  up  and 
label  the  mixture.  After  several  days,  test  once  more  with 
litmus  (?). 

This  action  of  water  is  found  to  be  greatly  hastened  by 
the  addition  of  free  acids,  although  the  acids  remain  them- 
selves unchanged  by  the  process.  Equivalent  quantities  (?) 
of  different  acids  show  very  different  accelerating  powers 
toward  this  reaction.  The  order  in  which  they  are  placed  by 
measurement  of  this  particular  form  of  activity,  however,  is 
the  same  as  that  into  which  they  fall  when  compared  by 
any  of  the  other  methods.  The  extent  to  which  the  change 
has  taken  place  can  be  measured  at  any  moment  by  titration 
with  alkali.  The  quantity  of  acid  which  was  present  at 
starting  being  known,  the  quantity  found  is  the  same  acid 
plus  the  acetic  acid  set  free  by  the  progress  of  hydrolysis. 
Subtraction  gives  the  quantity  of  the  latter,  and  this  quan- 
tity is  a  measure  of  the  activity  of  the  accelerating  acid. 
The  "  strengths "  of  hydrochloric  and  sulphuric  acids  are 
compared  in  b  by  this  method. 

6.  [Two  students  work  together.]  Procure  two  20  c.c. 
stoppered  graduated  flasks  and  a  10-c.c.  and  a  1  c.c.  pipette 
[Temp,  order].  Mark  the  flasks  so  as  to  be  able  to  distinguish 
them,  and  into  one  measure  exactly  10  c.c.  of  normal  (?) 
hydrochloric  acid,  and  into  the  other  10  c.c.  of  normal  (?) 


ACTIVITY   OF    ACIDS    MEASURED    CHEMICALLY          65 

sulphuric  acid.  Put  exactly  1  c.c.  of  methyl  acetate  into 
each,  and  fill  both  flasks  with  distilled  water  up  to  the  20  c.c. 
mark  at  once  (why  at  once?).  Stopper  the  flasks  tightly,  mix 
the  contents,  and  suspend  both  so  that  their  necks  are  just 
above  the  water  in  a  large  bath  heated  to  about  45°.  If  the 
bath  is  fairly  large,  further  external  heating  will  not  be  nec- 
essary. Otherwise,  maintain  the  temperature  by  means  of  a 
small  flame.  In  accurate  work  the  temperature  must  be  kept 
constant  within  0.1°  during  the  experiment  by  means  of  a 
thermostat.  Allow  the  flasks  to  remain  in  this  position  for 
half  an  hour.1 

While  this  is  going  on  make  some  normal  (or  approxi- 
mately normal,  =  4  per  cent.)  sodium  hydroxide  and  fill  a 
burette  with  it.  Take  fresh  portions  of  10  c.c.  of  each  of  the 
acids  and  titrate  them  with  the  alkali,  using  two  drops  of 
phenolphthalem  as  an  indicator.  Record  the  results.  These 
numbers  measure  the  amount  of  mineral  acid  at  starting  in 
each  flask. 

When  the  above  time  has  elapsed,  remove  both  flasks 
from  the  bath,  transfer  the  contents  of  each  to  a  separate 
beaker,  rinsing  out  the  flasks  with  distilled  water.  Add  two 
drops  of  phenolphthalein  to  each  portion  and  titrate  with  the 
solution  of  sodium  hydroxide  used  before.  The  difference 
between  the  volumes  of  alkali  required  for  the  neutralization 
of  10  c.c.  of  each  acid  with  and  without  methyl  acetate  repre- 
sents the  amount  of  sodium  hydroxide  required  to  neutralize 
the  acetic  acid  liberated  in  the  hydrolysis.  The  two  values 
obtained  are  functions  of  the  activity  of  the  acids.  Which 
acid  is  more  active?  What,  according  to  the  theory  of  ioni- 
zation,  is  really  measured  in  these  experiments  ?  What  does 
the  result  of  a  show  water  to  be  ? 

[Advanced  students].  To  learn  the  method  of  handling 
the  results  of  measurements  like  this,  so  as  to  get  a  numerical 
expression  for  the  relative  activity  of  acids,  some  work  on 
physical  chemistry  must  be  consulted. 

1  Instead  of  graduated  flasks  common  flasks  with  cork  stoppers 
may  be  used.  Measure  into  each  flask  10  c.c.  of  acid  and  then, 
with  the  same  pipette,  10  c  c.  of  water.  Add  the  1  c.c.  of  methyl 
acetate,  shake,  and  proceed  as  directed.  Another  action  which 
may  be  adapted  to  the  measurement  of  the  relative  activity  of 
acids  occurs  in  Chap.  XXII,  2,  a  (p.  96). 


CHAPTER   XV. 

OXIDES  AND  OXYGEN  ACIDS  OF  NITROGEN. 

1.  PRELIMINARY  EXPERIMENTS. 

a.  Nitric  acid  [Hood].  Place  a  few  grams  of  powdered 
sodium  nitrate  in  a  dry  retort  [Temp,  order]  or  distilling  flask, 
cover  it  with  concentrated  sulphuric  acid,  wait  till  the  sub- 
stances are  thoroughly  mixed,  and  then  distil  slowly.  Use 
the  sand  bath  as  a  means  of  heating  and  catch  the  distillate 
in  a  flask  partly  surrounded  by  water.  [CAUTION:  Use  the 
greatest  care  in  handling  this  liquid,  as  spilling  it  upon  the 
hands  may  lead  to  very  serious  wounds.] 

Describe  the  physical  properties  of  nitric  acid.  '  Deter- 
mine its  boiling  point  by  boiling  it  in  a  distilling  flask  and 
arranging  a  thermometer  so  that  it  is  immersed  in  the  vapor. 
Notice  the  color  of  the  acid.  Blow  some  air  through  the 
acid  ( ?).  To  what  was  the  color  due  ?  By  what  action  was 
the  colored  substance  produced?  What  property  of  nitric 
acid  does  this  indicate  ? 

6.  Invert  a  jar  of  water  in  the  pneumatic  trough  and  half 
fill  it  with  oxygen  from  the  iron  cylinder.  Dilute  the  nitric 
acid  prepared  above  with  an  equal  volume  of  water  in  a  small 
flask,  fitted  as  in  Fig.  10,  add  some  copper  turnings,  and,  after 
the  air  has  been  displaced,  bubble  the  gas  very  slowly  into 
the  oxygen  and  agitate  continually  with  water.  Notice  all 
the  results. 

Base  a  test  for  nitric  acid  on  this  experiment;  also  tests 
for  oxygen  and  for  nitric  oxide. 

c.  Using  these  results,  devise  a  way  of  determining  the 
proportion  of  oxygen  to  residual  gas  in  the  air  and  test  its 
accuracy  by  doing  the  experiment. 

d.  Action  of  heat  on  nitrates.    Heat  sodium  nitrate  in  a 
hard  glass  test-tube  ( ?).      Use  the  blast-lamp,  if  necessary. 
Test  the  escaping  gas  for  oxygen.     When  gas  ceases  to  be 
evolved,  preserve  the  residue  for  use  in  5,  a.    The  result  is 
typical  of  the  behavior  of  nitrates  of  alkali  metals. 

Heat  8-10  g.  of  powdered  lead  nitrate  in  a  hard  glass 
test-tube  and  conduct  the  gases  into  concentrated  (50  per 
cent.;  make  this  solution)  sodium  hydroxide  solution  in  a  test- 

66 


OXIDES    AND    OXYGEN    ACIDS    OF    NITROGEN  67 

tube.  Continue  heating  until  gas  is  no  longer  evolved.  What 
is  the  residue  in  the  hard  glass  tube?  The  result  is  typ- 
ical of  the  behavior  of  nitrates  of  heavy  metals.  Is  all  the 
gas  absorbed  by  sodium  hydroxide?  If  not,  test  the  escaping 
gas  for  oxygen.  Keep  the  sodium  hydroxide  solution  for  use 
in  5,  b. 

Cautiously  heat  some  ammonium  nitrate  [Care]  and  col- 
lect the  gas  in  a  bottle  over  water.  The  result  is  peculiar  to 
ammonium  nitrate.  Ignite  a  little  red  phosphorus  in  a 
deflagrating  spoon  and  plunge  it  into  the  gas(?).  What 
other  gas  is  suggested?  Suggest  a  test  that  would  enable 
you  to  distinguish  between  the  gases  (?).  What  change  in 
volume,  if  any,  will  accompany  this  combustion? 

Classify  nitrates  in  accordance  with  their  behavior  when 
heated. 

2.  PRINCIPLES  INVOLVED  IN  MAKING  NITRIC  ACID. 

a.  Was  nitric  acid  formed  on  mixing  sodium  nitrate  and 
sulphuric  acid  before  distillation  began  ?     Solve  this  question 
by  mixing  the    materials   (using  finely   powdered    sodium 
nitrate),  adding  a  very  little  water  [Caution],  agitating  for  a 
minute  or  so,  and  trying  the  test  in  1,  b. 

b.  Will  a  nitrate  alone  behave  in  the  same  way  toward 
copper?     Try  sodium  nitrate  solution  and  copper  (?). 

c.  Will   other  acids  behave  like   sulphuric  acid?     Try 
phosphoric  acid  with  powdered  sodium  nitrate,  as  in  a.     In 
view  of  the  result,  what  should  you  expect  to  pass  over  if  the 
mixture  with  phosphoric  acid  were  distilled? 

d.  Is  the  action  in  a  reversible?     To  answer  the  question 
take  a  few  c.c.  of   concentrated  sodium  hydrogen  sulphate 
solution  and  add  an  equal  or  greater  volume  of  pure  [Side- 
shelf]  concentrated  nitric  acid.    Cool  the  mixture  in  a  stream 
of  water  and  stir  with  a  glass  rod  ( ?).    [Failure  may  be  due  to 
the  solution  of  the  salt  not  being  sufficiently  concentrated.] 
Examine  the  result  with  a  lens.     What  is  formed?     If  the 
action    is    reversible,  write  the  equation  so  as  to  show  the 
existence  of  an  equilibrium.     What  enabled  us  to  obtain  a 
large  yield  of  nitric  acid  in  1,  a  in  spite  of  this? 

Give  other  instances  of  reversible  actions. 

3.  PROPERTIES  OF  NITRIC  ACID. 

a.  Is  its  solution  an  acid?    Prove  experimentally. 

b.  Recall  the  behavior  of  concentrated  and  of  dilute  sul- 
phuric acid  toward  metals,  and  of  the  former  toward  non- 
metals. 


68     OXIDES  AND  OXYGEN  ACIDS  OF  NITROGEN 

Try  the  action  of  (1)  magnesium  and  (2)  zinc  separately 
either  on  concentrated  or  on  dilute  nitric  acid,  and  that  of 
both  on  (3)  copper.  Explore  the  whole  action  thoroughly  in 
each  case  as  follows: 

Place  the  metal  in  a  side-neck  test-tube  (or  100  c.c.  flask), 
furnished  with  a  cork,  provided  with  a  dropping-funnel,  and 
fitted  with  a  delivery  tube.  Add  the  acid,  and  collect  the  gas 
over  water  after  the  air  has  been  displaced  from  the  appa- 
ratus. Observe  whether  nitrogen  tetroxide  is  formed  (?). 
Devise  a  way  of  separating  nitric  oxide  from  hydrogen,  in 
case  the  gas  collected  should  contain  any  of  the  latter.  (Why 
can  you  not  hope  to  recognize  the  hydrogen  by  its  combusti- 
bility without  separating  it  ?).  Examine  the  gas  for  each  of 
these  substances.  If  ammonia  is  formed  by  complete  reduc- 
tion of  the  nitric  acid,  where  will  it  be  found,  and  in  what 
condition  ?  (Consider  all  the  circumstances  carefully  or  you 
will  answer  wrongly.)  Test  for  its  presence  (?).  Isolate  the 
form  of  combination  which  the  metal  has  assumed,  by  evapo- 
rating the  solution  to  dryness  on  the  steam  bath  [Hood],  and 
determine  its  nature  (?).  In  view  of  the  action  of  nitrogen 
tetroxide  on  water  (1,  6),  explain  the  result  you  have  observed 
when  it  is  the  diluted  acid  that  is  used  with  a  metal.  Con- 
versely, the  result  with  concentrated  acid  is  explained  by  4,  a. 

c.  Try  the  action  of  tin  on  concentrated  nitric  acid  (?). 
When   the  action  has  exhausted  itself,  add  water  and  boil. 
Filter  through  a  small  filter  paper,  wash  the  precipitate  with 
water,  and  see  whether  a  neutral  filtrate  can  be  obtained  (?). 
Explain  what  you  observe.    Devise  a  way  of  showing  whether 
the  remaining  solid  is  a  nitrate  or  not,  and  try  it  ( ?). 

d.  Try  the  action  of  sulphur  on  concentrated,   boiling 
nitric  acid  (pure).     Is  there  any  evidence  of  action?     If  so, 
find  out  what  form  of  combination  the  sulphur  has  assumed  ( ?). 
Dilute  the  solution  with  water  before  adding  any  reagent. 

What  property  of  nitric  acid  seems  to  be  most  prom- 
inent? What  points  of  resemblance  and  of  difference  does 
nitric  acid  show  when  compared  with  sulphuric  acid? 

e.  Dip  a  piece  of  wool  in  concentrated  nitric  acid(?).    The 
yellow  coloring  matter  produced  is  xanthoproteic  acid. 

Give  the  three  chemical  properties  which  you  have  found 
to  characterize  nitric  acid. 

/.  Aqua  regia.  Add  concentrated  hydrochloric  acid  to 
nitric  acid,  warm,  and  notice  the  appearance  and  odor  ( ?). 
When  gold  and  platinum  (the  same  is  true  of  other  metals  a 
fortiori)  are  placed  in  aqua  regia  they  are  dissolved  and 
chlorides  are  formed.  These  metals  are  insoluble  in  dilute 


OXIDES  AND  OXYGEN  ACIDS  OF  NITROGEN     69 

acids  (see  table  of  solution  tensions,  p.  54,  8).  Explain  their 
solubility  in  this  mixture.  What  other  reagents  would  dis- 
solve them  on  the  same  principle  (p.  30, 1,  a)?  Which  of  the 
three  properties  of  nitric  acid  is  here  brought  into  play  ? 

4.  NITRIG  OXIDE. 

a.  Prepare  the  gas  by  the  action  of  copper  on  slightly 
diluted  nitric  acid  in  a  side-neck  test-tube.     Pass  the  gas 
through  warm  concentrated  nitric  acid  (?).     What  change  is 
produced  in  the  gas  by  the  acid?     Use  this  result  to  account 
for  the  product  of  the  action  of  a  metal  on  concentrated,  as 
distinguished  from  dilute,  nitric  acid  (cf.  3,  b). 

b.  Prepare  a  solution  of  ferrous  ammonium  sulphate  and 
divide  into  four  parts.     [The  double  salt  is  supplied  in  the 
laboratory  instead  of  ferrous  sulphate  simply  because  it  keeps 
better.     The  ammonium  sulphate  may  be  disregarded  here.] 

Pass  the  gas,  which  must  be  colorless,  through  onepart(?). 

c.  Acidify  the  second  portion  of  the  ferrous  ammonium 
sulphate  solution  with  sulphuric  acid,  heat  to  boiling,  and  add 
nitric  acid  drop  by  drop  (mix  after  each  drop),  until  there  is 
no  further  action.     To  ascertain  what  the  solution  contains, 
add  ammonium  hydroxide  ( ?).     Obtain  the  information  neces- 
sary to  explain  the  action  by  adding  ammonium  hydroxide  to 
the  third  portion  of    the  ferrous  solution  ( ?)  and  to  ferric 
chloride  solution  (?).     What  change  did  the  nitric  acid  pro- 
duce in  the  diferrion  (cf.  p.  55,  9)? 

d.  Delicate  test  for  nitric  acid,  or  a  nitrate.     Add  a  very 
little  sodium  nitrate  solution  to  2-3  c.c.  of  the  ferrous  solution 
in  a  test-tube  and  pour  concentrated  sulphuric  acid  steadily 
down  the  side  of  the  tube  so  that  it  may  form  a  layer  at  the 
bottom.    Notice  the  brown  ring  and  explain  with  the  help  of 
the  above  results. 

5.  NITROUS  ACID. 

a.  Dissolve  in  a  few  drops  of  water  the  residue  from  heat- 
ing sodium  nitrate  in  1,  d.     If  it  is  necessary  to  repeat,  melt 
the  nitrate  with  a  piece  of  lead  in  a  crucible  and  stir  with  a 
file(?).     This  gives  the  same  product  more  easily  (why?). 
To  the  highly  concentrated  aqueous  extract,  add  dilute  sul- 
phuric acid.     Contrast  the  action  with  that  on  a  nitrate  (?). 

b.  Examine  the  solution,  obtained  by  passing  the  gases 
from  lead  nitrate  into  sodium  hydroxide  in  1,  d,  for  nitrite,  by 
acidifying  (test?)  with  the  minimum  amount  of  concentrated 
sulphuric  acid  ( ?).     Add  a  drop  of  this  mixture  to  some  starch 
emulsion  containing  a  drop  or    two  of    potassium  iodide 


70  OXIDES    AND    OXYGEN    ACIDS    OF    NITROGEN 

solution  (?).  To  a  small  portion  of  the  same  mixture  add  a 
drop  of  diluted  potassium  permanganate  solution  ( ?).  What 
substance  is  shown  to  be  present  by  these  three  reactions  ? 
Try  these  three  tests  with  a  concentrated  solution  of  sodium 
nitrite  ( ?). 

Boil  the  remainder  of  the  acidified  mixture  until  red 
fumes  cease  to  be  evolved.  Then  insert  a  piece  of  copper  (?). 
What  substance  is  shown  to  be  present  by  this  reaction? 
Combining  these  results,  what  do  you  infer  was  the  action  of 
nitrogen  tetroxide  on  sodium  hydroxide? 


CHAPTER  XVI. 

PHOSPHORUS,  ARSENIC,  ANTIMONY,  BISMUTH. 

1.  PHOSPHORUS.     What  difference  in  behavior  do  the  two 
allotropic  modifications   of  phosphorus  exhibit  [R].     What 
is   formed  when  phosphorus   unites   directly  with   oxygen? 
Answer  from  previous  knowledge. 

2.  PHOSPHINE  [Hood].   Place  a  small  piece  of  calcium  phos- 
phide in  water  or  dilute  hydrochloric  acid  in  a  beaker  (?). 
Relate  this  to  ways  of  making  other  hydrides  of  non-metals 
(e.  g.,  ammonia,  hydrogen  sulphide,  and  acetylene)  from  com- 
pounds of  the  non-metal  with  a  metal.     In  what  ways  does 
phosphine  differ  from  ammonia  [R]? 

3.  HALIDES  OF  PHOSPHORUS  [Hood].     The  actions  of  water 
on  the  tribromide  and  tri-iodide  (p.  39,  3),  have  already  been 
noticed. 

a.  Place  1  c.c.  of  phosphorus  trichloride  [Store-room]  in 
a  test-tube  (?).  Blow  the  breath  over  the  mouth  of  the 
tube  (?).  Add  water  a  drop  at  a  time  (?).  Add  more  water 
and  boil.  Pass  hydrogen  sulphide  through  the  solution  (?). 
'  6.  Place  a  few  small  granules  of  phosphorus  pentachloride 
on  a  watch  glass.  Blow  the  breath  over  it  (?).  Throw  it  into 
some  water  in  a  test-tube  (?)  and  boil.  To  part  of  the 
solution  add  excess  of  silver  nitrate  solution  (?).  Filter. 
What  remains  on  the  filter?  To  the  filtrate  add  ammonium 
hydroxide  drop  by  drop  ( ?).  The  nature  of  this  precipitate 
is  learned  in  4,  a. 

4.  PHOSPHORIC  ACID. 

a.  Heat  a  very  little  red  phosphorus  with  excess  of  slightly 
diluted  nitric  acid  ( ?).     When  the  action  has  ceased,  filter,  if 
necessary,  and  drive  off  the  water  and  excess  of  nitric  acid 
from  the  filtrate  on  the  steam  bath  (?).    Re-dissolve  in  water 
the  sirup  which   remains.     Test   the  solution   with   litmus 
paper  (?).     Add  silver  nitrate  solution.     The  precipitate  is 
silver  orthophosphate  (a  black  precipitate,  due  to  the  pres- 
ence of  phosphorous  acid,  may  sometimes  be  formed).    What 
was  the  acid  [RJ  ? 

b.  Throw  a  pinch  of  phosphorus  pentoxide,  in  minute 
portions  at  a  time,  into  cold  distilled  water  in  a  test-tube  (?). 


72          PHOSPHORUS,    ARSENIC,    ANTIMONY,    BISMUTH 

Allow  the  solution  to  stand  for  a  few  minutes,  or  until  it 
becomes  clear.  Add  silver  nitrate  solution  (?).  What  acid 
was  formed  [R]? 

5.  PHOSPHATES. 

a.  Test  some  sodium  phosphate  (secondary  sodium  ortho- 
phosphate)   solution   with   neutral   litmus   paper  (?).      Add 
silver  nitrate  solution  ( ? )  until  the  precipitation  is  complete. 
Test  the  filtrate  from  this  with  litmus  again  (?).     Are  acid 
salts  always  acid  toward  litmus?     If  not,  explain  wrhy  they 
are  not. 

Add  excess  of  ammonium  chloride  and  a  little  ammonium 
hydroxide  solution  to  magnesium  sulphate  solution.  Add 
some  of  this  u  magnesia  mixture  "  to  diluted  sodium  phosphate 
solution  ( ?).  Describe  the  precipitate. 

b.  Heat   a   little   dry   sodium    phosphate   in  a    crucible 
strongly  [Blast-lamp]  for  twenty  minutes,  or  until  every  part 
of  the  substance  has  been  affected  and  no  further  change  is 
observed  (?).     When  the  residue  is  cold,  dissolve  it  in  water 
and  add  silver  nitrate  solution  (?).     Contrast  with  the  pre- 
cipitate from  unignited  phosphate  (5,  a)  and  compare  with 
that  in  4,  b. 

c.  Heat  a  little  microcosmic  salt  strongly  in  a  porcelain 
crucible,  using  the  same  precautions  as  above,  and  notice  its 
behavior  and  odor  (?).     Dissolve  the  residue  in  water  and  add 
silver  nitrate  solution  (I). 

Make  a  bead  of  microcosmic  salt  on  a  platinum  wire  and 
fuse  with  it  a  single  minute  particle  of  cupric  oxide  (?). 

What  difference  do  your  experiments  show  between  the 
stabilities  of  sodium  metaphosphate  and  sodium  nitrate  (p.  66, 
!,<*)? 

6.  ARSENIC. 

a.  Heat  a  particle  of  arsenic  on  a  crucible  lid  ( ?).    Notice 
its  behavior  and  the  odor.     Do  the  same  with  a  particle  of 
realgar  (?). 

b.  Boil  a  little  (0.3  g.)  powdered  arsenic  with  excess  of 
nitric  acid.      What   evidence    is  there  of  action  (cf.  4,  a)? 
Preserve  the  solution  for  examination  under  9.     [Do  8  next 
and  then  return  to  7.] 

7.  ARSENIC  [Hood.  CARE!  POISON!].     Arrange  a  side-neck 
test-tube  with  safety  and  delivery  tubes  and  nozzle  to  generate 
and  burn  hydrogen.     Place  in  it  a  piece  of  chemically  pure 
zinc  and  add  pure  hydrochloric  acid  [Side-shelf].     When  the 
air  has  been  displaced  [Care.  Test  ?],  light  the  gas  and  hold  a 


PHOSPHORUS,    AESENIC,    ANTIMONY,    BISMUTH          73 

crucible  lid  in  the  flame  ( ?).  If  there  is  no  deposit,  add  a 
drop  or  so  of  the  solution  of  arsenic  trichloride  (8,  6),  observe 
the  appearance  of  the  flame,  and  obtain  a  deposit  on  the 
crucible  lid  ( ?).  What  kind  of  chemical  change  takes  place 
in  the  flame  (cf.  p.  57,  2,  &)?  Heat  the  tube,  through  which 
the  gas  passes  to  the  nozzle,  with  a  Bunsen  flame  ( ?  Marsh's 
test).  When  these  experiments  are  completed,  fill  the  test- 
tube  with  water  to  stop  the  action. 

Describe  the  appearance  of  the  deposit  (?). 

Apply  fresh  bleaching  powder  solution  to  the  deposit  on 
the  crucible  lid  by  means  of  a  glass  rod  (?). 

What  way  of  making  arsine  is  identical  in  principle  with 
that  used  for  phosphine  in  2  [R]? 

How  do  ammonia  and  phosphine  behave  when  heated  [R]  ? 

8.  ARSENIC  TRIOXIDE  (ARSENIOUS  ANHYDRIDE). 

a.  Boil  a  pinch  of  the  trioxide  with  sodium  hydroxide 
solution  ( ?).    To  what  class  of  oxides  does  this  one  appear  to 
belong  ? 

b.  Boil  a  pinch  of  the  trioxide  with  concentrated  hydro- 
chloric acid  (?).     Dilute  with  a  little  water  and  keep  part  of 
the  solution  for  7.     To  what  class  of  oxides  does  it  appear 
now  to  belong? 

Pass  hydrogen  sulphide  from  a  Kipp's  apparatus  through 
the  rest  of  the  solution  (?)  until  it  is  saturated  (test  ?).  Recall 
result  of  3,  a  and  compare  ( ?).  Filter,  reject  the  filtrate,  and 
pour  hot  colorless  or  yellow  ammonium  sulphide  solution  on 
the  precipitate  [R]  (?).  Acidify  (test  ?)  with  hydrochloric  acid 
the  solution  in  ammonium  sulphide  which  runs  through  ( ?). 

c.  Seal  one  end  of  a  small  piece  of  glass  tubing.     Mix  a 
pinch  of  the  trioxide  with  a  little  powdered  wood  charcoal. 
Place  some  of  the  mixture  in  the  bottom  of  the  tube,  with  a 
little  fresh  wood  charcoal  above,  and  heat  strongly  ( ?). 

'  9.  ARSENIC  ACID.  Neutralize  the  solution  of  arsenic  in 
nitric  acid  (6,  6)  with  ammonium  hydroxide,  avoiding  excess. 
Divide  into  two  parts.  To  the  first  add  silver  nitrate  solu- 
tion ( ?).  To  the  second  add  "  magnesia  mixture  "  ( ?).  Recall 
5,  a,  and  compare. 

10.  ANTIMONY.     Behavior  similar  to  that  of  arsenic. 

11.  STIBINE.     Follow  all  directions  in  7,  using  antimony 
trichloride  solution  in  place  of  that  of  arsenic  trichloride. 

12.  ANTIMONY  TRICHLORIDE. 

a.  Place  some  of  the  crystals  in  a  test-tube  and  add  a 
little  water  (?).  Test  the  liquid  with  litmus  paper  (?).  Add 


74         PHOSPHORUS,    AESENIC,    ANTIMONY,    BISMUTH 

more  water,  warm,  and  make  a  clear  solution  by  adding  small 
quantities  of  concentrated  hydrochloric  acid  (?),  agitating 
vigorously  after  each  addition. 

b.  To  half  of  this  solution  add  a  large  amount  of  water 
[R]  (?).     What   kind  of  action  is  this?     Add  concentrated 
hydrochloric  acid  again  ( ?).     How  does  this   illustrate   the 
influence  on  a  reversible  action  of  change  in  concentration  of 
one  factor  ?     Write  the  equation  which  combines  both  actions. 

How  could  you  show  that  the  molecules  of  the  trichloride  are 
only  partly  hydrolyzed  by  water,  leaving  a  basic  salt  (with 
phosphorus  trichloride  the  hydrolysis  was  complete)? 
What  is  the  significance  of  this  difference  [R]  ? 

c.  Through  the  rest  of  the  trichloride  solution  pass  hydro- 
gen sulphide  from  a  Kipp's  apparatus  (?)  to  saturation  (test  ?). 
Filter,  reject  the  nitrate,  and  pour  hot  yellow  ammonium  sul- 
phide solution  on  the  precipitate  [R]  ( ?).     It  may  be  better  to 
scrape  the  precipitate  into  a  beaker  and  boil    it  with  the 
reagent.     Acidify  with  excess  of  hydrochloric  acid  the  solu- 
tion in  ammonium  sulphide  (?). 

13.  ANTIMONY  TRIOXIDE.     Heat  some  powdered  antimony 
with  concentrated  nitric  acid(?).     How  could  you  ascertain 
whether  the  result  was  a  nitrate  or  not  ?    How  does  this  differ 
from  the  behavior  of  arsenic  (6,  b)  [R]?     Filter. 

Boil  one-half  of  the  powder  with  hydrochloric  acid  ( ?).  What 
kind  of  oxide  does  the  result  show  it  to  be? 

Boil  the  other  half  with  sodium  hydroxide  solution  (?). 
What  kind  of  oxide  does  this  show  it  to  be? 

14.  BISMUTH.    Prepare  a  match   as  in   Chap.  XIII,   12 
(match  test).    Place  on  the  end  a  moistened  mixture  of  bis- 
muth nitrate  and  anhydrous  sodium  carbonate  and  heat  in 
the  reducing  region  of  a  small  Bunsen  flame.     Break  up  the 
charred  match  gently  in  water  in  the  mortar,  wash  away  the 
lighter  particles,  and  examine  the  residue  ( ?). 

15.  SALTS  OF  BISMUTH. 

a.  Add  water  to  some  crystals  of  bismuth  nitrate  in  a  test- 
tube  (?).     Obtain  a  clear  solution  by  adding  small  quantities 
of  concentrated  nitric  acid. 

b.  To  one-half  of  the  solution  add  a  large  amount  of 
water  (?).    Write  the  equation  to  show  that  an  equilbrium 
exists. 

If  difficulty  is  found  in  obtaining  a  precipitate  with  water 
and  the  nitrate,  make  a  clear  solution,  as  in  a,  with  the  help 
of  hydrochloric  acid  and  then  dilute  with  water. 


PHOSPHORUS,    ARSENIC,    ANTIMONY,    BISMUTH         75 

c.  Dilute  the  remainder  of  the  solution  from  a  with  water 
and  pass  hydrogen  sulphide  through  it  ( ?).  Filter  and  dis- 
card the  filtrate.  Treat  the  precipitate  with  warm  yellow 
ammonium  sulphide.  Filter  and  acidify  this  filtrate.  What 
is  precipitated?  Was  the  bismuth  sulphide  dissolved? 
Compare  the  result  with  that  in  8,  b  and  12,  c.  How  could 
you  separate  the  sulphides  of  arsenic  and  antimony  from  that 
of  bismuth  I 


CHAPTER    XVII. 

CARBON. 

1.  CHARCOAL. 

a.  Place  a  small  piece  of  charcoal  in  a  test-tube  half  full 
of  water  (?).  Now  sink  it,  if  necessary,  with  copper  wire  and 
boil  the  water  for  several  minutes  ( ?).  When  the  whole  has 
cooled,  test  once  more  the  tendency  of  the  charcoal  to  float  (?). 
Explain. 

6.  Boil  dilute  solutions  of  litmus  and  indigo,  separately, 
with  powdered  animal  charcoal  and  filter  each  liquid  ( ?).  The 
activity  of  the  charcoal  is  much  increased  by  previous  heating 
in  a  covered  crucible. 

c.  In  a  hard  glass  test-tube  mix  intimately  2  g.  of  powdered 
cupric  oxide  with  1  g.  of  powdered  wood  charcoal  and  heat 
[Blast-lamp].  Pass  the  gases  through  lime  water  (?).  Exam- 
ine the  residue  by  rubbing  it  in  the  mortar  and  washing  away 
the  lighter  particles  ( ?). 

2.  CARBON  DIOXIDE. 

a.  Fit  up  a  generating  flask  with  a  safety  tube  and  con- 
nect with  two  wash  bottles  containing  water  and  concentrated 
sulphuric  acid  respectively  (what  is  the  use  of  each  of  these? 
The  latter  is  unnecessary  if  3  is  omitted).     Place  in  the  flask 
some  pieces  of  marble  and  pour  upon  them  diluted  hydro- 
chloric acid.     Collect  the  gas  in  three  bottles  by  upward  dis- 
placement of  air. 

b.  Use  the  first  to  ascertain  whether  the  g;:s  is  soluble  in 
water  or  not. 

Use  the  second  to  compare  its  weight  with  that  of  air. 
Use  baryta  water  or  lime  water  as  a  test. 

Use  the  third  to  test  its  power  of  supporting  combustion. 

c.  Lead  the  gas  into  a  little  sodium  hydroxide  solution  in 
a  test-tube  until  the  solution  is  saturated  (test  ?).     Let  the 
solution  dry   spontaneously   (first   residue).      Heat  the  dry 
residue  (?)  in  a  test-tube  and  determine  what  two  things  are 
given  off. 

To  this  residue  after  heating  (second  residue)  add  dilute 
hydrochloric  acid  until  all  action  ( ?)  ceases.  Evaporate  the 
solution  on  the  steam  bath  and  examine  and  taste  this  final 
residue  ( ?). 

76 


CARBON  77 

Having  recognized  the  products  of  the  last  action  and 
taking  into  account  the  preceding  observations,  state  what 
the  nature  of  the  second  and  first  residues  must  have  been. 
Write  equations  for  all  actions. 

3.  MOLECULAR  WEIGHT  OF  CARBON  DIOXIDE  [Quant.].    Deter- 
mine the  weight  of  1  liter  of  the  gas  by  the  method  used  for 
sulphur  dioxide  (p.  61,  8),  and  calculate  the  weight  of  the 
gram-molecular  volume  at  0°    and  760  mm.      What   further 
information  must  we  have  to  enable  us  to  determine  the 
formula  ? 

Use  the  quantitative  results  you  obtained  in  the  synthesis 
of  carbon  dioxide  (p.  15,  1),  along  with  this  molecular  weight, 
to  calculate  the  weights  of  carbon  and  of  oxygen  in  a  molec- 
ular weight  of  the  gas.  What  further  steps  are  necessary 
in  order  to  fix  the  atomic  weight  of  carbon? 

4.  CARBON  MONOXIDE. 

a.  Heat  about  10  g.  of  oxalic  acid  crystals  with  concen- 
trated sulphuric  acid  in  a  generating  flask  and  fill  a  bottle 
with  the  gas  which  is  given  off.  Shake  with  lime  water  (?). 
With  what  substance  should  we  wash  the  gas  to  remove  the 
carbon  dioxide?  Arrange  a  wash  bottle  to  purify  the  gas. 
Fill  two  bottles  with  the  purified  gas  over  water,  Test  one 
with  lime  water  again  ( ?).  If  the  gas  is  pure,  burn  that  in  the 
other  bottle,  add  lime  water  at  once,  close  quickly  and 
shake  (?). 

6.  Devise  a  way  of  ascertaining  roughly  the  relative  vol- 
umes of  the  two  gases  generated  in  a  and  measure  the  pro- 
portion in  a  test-tube  full  of  the  mixed  gases. 

5.  MOLECULAR    WEIGHT    OF    CARBON    MONOXIDE    [Quant.]. 
Arrange  a  250  c.c.  flask  as  in  Fig.  3,  using,  however,  a  round- 
bottomed  flask  for  the  purpose.     Make  a  mark  on  the  neck  at 
the  bottom  of  the  stopper,  so  as  to  be  able  to  measure  the 
exact  content  of  the  flask  up  to  the  stopper.     Place  30  c.c.  of 
water  in  the  flask,  remove  the  clip,  which  must  be  a  strong 
one,  and  boil  the  water  with  a  small  flame  for  about  five 
minutes,  so  as  to  drive  out  all  the  air.    Close  the  rubber  tube 
with  the  clip  and  remove  the  flame  quickly,  wipe  the  flask  and 
allow  it  to  cool.     When  it  has  assumed  the  temperature  of 
the  air,  weigh  the  whole  carefully,  suspending  the  apparatus 
on  the  balance  by  a  wire.    Connect  with  the  apparatus  deliver- 
ing pure  carbon  monoxide,  and  open  the  clip  a  very  little  so 
as  to  admit  a  slow  stream  of  the  gas.     When  the  flask  is  full, 
close  the  clip,  disconnect  from  the  generating  apparatus,  open 
the  clip  for  an  instant  to  restore  the  pressure  to  that  of  the 


78  CARBON 

atmosphere  and  weigh  again.  The  gain  in  weight  represents 
the  weight  of  the  carbon  monoxide.  Read  the  barometer  and 
thermometer.  Subtract  from  the  barometric  reading  the 
aqueous  tension  at  the  observed  temperature.  Ascertain  the 
volume  of  the  flask  by  filling  with  water  to  the  mark  and 
weighing  again. 

Calculate  the  weight  of  1  liter  and  of  the  gram-molecular 
volume  of  the  gas  at  0°  and  760  mm. 

To  what  class  of  gases  would  this  method  of  determining 
the  density  and  molecular  weight  be  applicable  ?  Why  could 
not  this  method  be  used  for  carbon  dioxide? 

6.  ACIDS. 

a.  Add  some  dilute  sulphuric  acid  to  sodium  acetate  and 
warm.     Notice  the  odor.     How  could  you  obtain  acetic  acid? 
How  is  it  manufactured  [R.  Organic  chemistry]? 

b.  Take  some  acetic  acid  and  test  its  reaction  with  lit- 
mus (?).    Recall  its  action  on  iron  (p.  22, 1, d).     Add  1  g.  of 
litharge  (lead  monoxide)  to  2.5  c.c.  of  acetic  acid  and  boil  (?). 
Filter,  if  necessary,  and  set  the  clear  solution  aside  to  crystal- 
lize.   Describe  the  product.     What  is  its  common  name  [R]? 

7.  ALCOHOL.     Dissolve  20  g.  of  molasses  in  150  c.c.  of 
water  and  add  a  little  yeast.    Fill  a  flask  to  the  base  of  the 
neck  with  the  mixture,  plug  the  mouth  loosely  with  cotton, 
and  set  the  whole  aside  for  3-4  days.     At  the  end  of  this  time 
warm  the  solution  and  test  the  gas  which  is  given  off  for  car- 
bon dioxide  [R]. 

Set  up  a  condenser  [Temp,  order]  and  distilling  flask 
(Fig.  16).  Filter  the  liquid  and  distil  off  about  50  c.c.,  using 
an  ordinary  flask  connected  with  the  condenser  by  an  L  tube. 
Boil  this  portion  in  the  distilling  flask  with  a  small  flame  and 
catch  the  part  which  passes  over  between  80°  and  93°. 

Notice  the  odor  of  the  distillate  (?).  Test  its  reaction 
with  neutral  litmus  paper  (?).  Use  one  drop  to  ascertain 
whether  it  burns.  To  the  rest  add  a  crystal  of  iodine  and 
enough  sodium  hydroxide  solution  to  dissolve  it.  Shake 
vigorously  and  do  not  add  more  alkali  than  is  absolutely 
necessary.  Warm  the  solution  and  then  cool  it  ( ?).  This  is 
the  iodofonn  test. 

8.  ESTERS.     Why  is  the  name  "ethereal  salts,"  commonly 
given  to  these  substances,  inconsistent  with  the  definition 
of  a  salt  [R]  ? 

a.  Dissolve  about  1  g.  of  sodium  acetate  in  a  very  little 
water,  add  a  few  drops  of  concentrated  sulphuric  acid  and 


CARBON  79 

two  or  three  drops  of  alcohol  Warm  and  notice  the  odor 
[R].  This  is  used  as  a  test  for  acetic  acid. 

b.  Place  in  a  porcelain  dish  a  piece  of  fat  the  size  of  a 
pea,  and  add  2  c.c.  of  alcohol  and  five  drops  of  50  per  cent, 
sodium  hydroxide  solution.  Stir  constantly  and  boil  very 
gently  until  the  odor  of  alcohol  is  no  longer  perceptible, 
then  stop.  The  alcohol  is  used  as  a  common  solvent  for  the 
fat  and  the  alkali.  What  is  the  residue  [R]  ? 

Dissolve  the  soap  in  hot  water,  cool,  and  to  half  of  the 
solution  add  dilute  hydrochloric  acid  and  shake  vigorously  (?). 
Withdraw  the  floating  coagulum  by  means  of  a  glass  rod, 
suspend  it  in  water  in  a  test-tube,  add  a  few  drops  of  sodium 
hydroxide,  and  heat  until  solution  takes  place.  What  do  you 
conclude  from  its  solubility  in  alkali? 

To  the  other  half  of  the  soap  solution  add  calcium 
chloride  solution  (?).  Explain  the  action  of  hard  water  [R] 
on  soap  solution. 

9.  HYDROCARBONS. 

a.  Powder  some  fused  sodium  acetate  and  some  sodium 
hydroxide  and  mix  them  intimately  in  approximately  equal 
proportions.     Then  add  a  little  powdered  quicklime  and  iron 
filings  (these  are  not  necessary  for  the  chemical  action  in 
itself),  and  mix  again.     Heat  the  mixture  in  a  hard  glass  test- 
tube  clamped  in  a  horizontal  position  and  fitted  with  a  cork 
and  deliver}7  tube.     Catch  some  of  the  gas  in  a  bottle  by  dis- 
placement of  water,  and  explode  it  with  air  ( ?).     Burn  the 
gas  in  a  jet  and  note  the  degree  of  luminosity  of  the  flame  (?). 
Consider  how  you  will  ascertain  what  it  forms  in  burning, 
and  try  experiments  to  settle  the  matter. 

b.  Fit  a  250  c.c.  flask  with  a  doubly  bored  cork,  through 
which  pass  a  dropping-funnel  and  L  tube,  and  connect  with 
an  empty  bottle  (why  ?)  provided  with  a  doubly  bored  cork 
through  which  pass  an  L  tube  and  a  tube  drawn  out  to  a 
nozzle.    Place  in   the  flask  5-10  g.   of  dry,  broken  glass. 
Clamp  the  flask  upon  the  ring  stand  over  a  sand  bath.   When 
the  whole  apparatus  is  ready,  and  its  airtightness  has  been 
ascertained  (and  not  until  then),  put  about  5  g.  of  phosphorus 
pentoxide  into  the  flask  and  close  it  quickly  (why?).    Mix  the 
pentoxide  with  the  broken  glass  by  shaking,  and  set  the  flask 
in  position  again.     Introduce  into  the  bulb  of  the  dropping- 
funnel  some  alcohol.    Finally  heat  the  pentoxide  and,  when 
it  has  had  time  to  reach  150-170°,  admit  the  alcohol  a  drop 
or  two  at  a  time  to  the  flask. 

When  the  air  in  the  apparatus  has  been  displaced,  fill  a 
narrow-mouthed  bottle,  provided  with  a  rubber  or  greased 


80  CARBON 

glass  stopper,  with  the  gas  (?)  by  downward  displacement 
of  air. 

Add  a  drop  of  bromine  [Hood]  to  the  gas  and  replace  the 
stopper  instantly.  Observe  what  happens,  and,  after  a  min- 
ute, open  the  bottle  under  water  ( ?)  [RJ. 

Burn  a  jet  of  the  gas  and  observe  the  degree  of  luminosity 
of  the  flame. 

Why  is  the  accepted  formula  for  this  gas  preferred  to  the 
simplest?  What  volume  of  oxygen  would  be  required  to 
burn  a  volume  of  the  gas  completely  ?  What  would  be  the 
volumes  of  the  products  ? 


CHAPTER  XVIII. 

SILICON    AND   BORON. 

1.  SILICA.  Mix  1  g.  of  finely  powdered  silica  with  4-5  g. 
of  anhydrous  sodium  carbonate.  Make  a  small  watch-spring 
spiral  on  the  end  of  the  platinum  wire  [Instructions]  and, 
by  alternately  heating  in  the  Bunsen  flame  or  blast-lamp,  and 
dipping  in  the  mixture,  obtain  a  large  bead  and  heat  it 
strongly  till  all  action  ( ?)  seems  to  have  ceased.  Place  the 
bead  in  a  test -tube  and  make  others  by  the  same  process. 
Dissolve  the  beads  in  a  small  amount  of  water.  Add  hydro- 
chloric acid  a  drop  at  a  time  until  the  solution  is  strongly 
acid  (?).  Evaporate  the  solution  to  dryness  on  the  sand 
bath  ( ?).  Treat  the  residue  with  warm  water,  wash  the  whole 
contents  of  the  dish  into  a  test-tube  and  examine  ( ?). 

2.  A  SILICATE.  Mix  dry  potassium  carbonate  with  anhy- 
drous sodium  carbonate  in  equal  proportions  in  a  mortar.  Coil 
the  platinum  wire  to  watch-spring  form.  Mix  a  little  pow- 
dered talc  (is  this  soluble  in  water?  What  is  its  common 
name?)  with  6-7  times  as  much  of  the  "fusion  mixture"  and 
hold  some  of  the  result  on  the  platinum  wire  in  the  flame  of 
the  blast-lamp  till  it  is  completely  melted  and  all  action  (?) 
has  ceased.  Repeat  till  several  beads  are  obtained.  Treat  the 
beads  with  boiling  water  in  a  test-tube  until  they  are  com- 
pletely disintegrated.  Filter  through  a  small  filter  paper  and 
wash  the  precipitate  with  water.  Preserve  this  filter  paper 
and  precipitate  for  use  later.  Acidify  the  filtrate  with  con- 
centrated hydrochloric  acid  and  proceed  as  in  1. 

Make  a  hole  in  the  paper  and  wash  the  precipitate 
obtained  above  into  a  test-tube.  Add  dilute  hydrochloric 
acid  and  warm  ( ?).  Filter,  if  necessary,  and  add  ammonium 
hydroxide  to  alkaline  reaction  ( ?)  The  precipitate  is  alumin- 
ium hydroxide.  Boil  and  filter.  To  the  filtrate  add  a  few 
drops  of  ammonium  hydroxide,  some  ammonium  chloride 
solution  and  some  sodium  phosphate  solution  and  shake  ( ?). 
Compare  with  Chap.  XVI,  5,  a  (p.  72). 

3.  BORIC  ACID. 

a.  Dissolve  some  borax  in  distilled  water.  Test  this  solu- 
tion and  a  sample  of  the  distilled  water  simultaneously  with 

81 


82  SILICON    AND    BOKON 

neutral   litmus   paper,   and,  by  comparing  tints,  determine 
whether  the  solution  has  any  reaction  ( ?). 

Put  two  drops  of  the  solution  into  a  test-tube  and  dilute 
with  water  till  the  tube  is  two-thirds  full.  To  the  remainder 
add  silver  nitrate  solution  ( ?).  Add  silver  nitrate  solution  to 
the  very  dilute  solution  also  (?).  The  difference  is  more 
marked  if  the  dilute  solution  is  first  warmed.  For  compari- 
son, add  silver  nitrate  solution  to  an  exactly  equally  diluted 
sodium  hydroxide  solution  (?).  What  conclusion  do  you 
draw  in  regard  to  the  action  of  water  on  borax  ?  Write  the 
equation.  Is  the  action  reversible  [R]  ? 

b.  Make  a  strong  solution  of  borax  in  boiling  water  in  a 
test-tube.      Add  concentrated  hydrochloric  acid  until  the 
solution  is  strongly  acid  and  set   aside  to  cool  (?)    Filter, 

Sress  out  the  mother  liquor,  and  wash  the  crystals  with  a  few 
rops  of  cold  water.     Dissolve  in  the  minimum  amount  of 
boiling  water  and  set  aside  again.    Filter,  and  wash  the  crys- 
tals as  before. 

Dissolve  part  of  the  crystals  in  hot  water  and  test  the 
reaction  of  the  solution  with  neutral  litmus  paper,  using  the 
same  precaution  as  in  a  ( ?).  What  conclusion  do  you  draw 
in  regard  to  boric  acid?  Dip  a  strip  of  turmeric  paper  in  the 
same  solution,  wrap  it  round  the  upper  part  of  the  test-tube 
and  boil  the  solution  until  the  paper  is  dry  ( ?)  Touch  it  with 
a  glass  rod  dipped  in  sodium  hydroxide  solution  (?).  This 
is  a  test  for  boric  acid. 

Treat  the  rest  of  the  crystals  with  cold  sodium  hydroxide 
solution  (?).  Explain  the  formation  of  boric  acid  and  its 
solubility  in  bases  according  to  the  ionic  theory. 

c.  Place  on  separate  parts  of  a  watch  glass  a  drop  of  con- 
centrated sulphuric  acid,  a  drop  of  glycerine,  and  a  very  little 
powdered  borax.     Rub  the  end  of  a  platinum  wire  in  each  of 
these.    Bring  the  end  of  the  wire  slowly  up  to  the  outer  edge 
near  the  bottom  of  a  small  Bunsen  flame.     How  is  the  flame 
colored?    This  is  a  test  for  a  borate. 


CHAPTER  XIX. 

METALS  OF  THE  ALKALIES. 

1.  POTASSIUM  HYDROXIDE. 

a.  Dissolve  about  30  g.  of  potassium  carbonate  (what  is 
the  source  of  this  salt  ?)  in  200-300  c.c.  of  water  in  a  large  beaker 
and  heat  to  boiling.     Slake  15-20  g.  of  quicklime  in  a  beaker 
( ?),  using  heat  if  necessary  to  start  the  action,  and  make  the 
product  into  a  very  thin  paste  with  water.     Add  this  grad- 
ually, and  with  constant  stirring,  to  the  boiling  solution  (?). 
Continue  boiling  for  a  few  minutes.    (Why  are  iron  utensils 
exclusively  employed  in  this  operation  when  it  is  performed 
on  a  large  scale  [R]  ?)    Let  the  solution  settle  and,  when  it  is 
cold,  decant  the  clear  liquid.     Use  the  solution  in  b  and  c. 

What  kind  of  hydroxides  alone  can  be  made  by  this 
method?  Which  hydroxides  are  of  this  kind  [R]? 

b.  Alkalimetry.    Find  the  strength  of  this  solution  by 
titration.     To  do  this,  place  a  carefully   measured  volume 
(about  10  c.c.)  of  the  clear  solution  in  a  small  flask.     Dilute 
with  about  four  times  its  volume  of  water,  as  the  concentrated 
solution  is  apt  to  decompose  the  indicator.    Fill  a  burette 
with  "  normal "  hydrochloric  acid.     Add  some  phenolphtha- 
lem  solution  to  the  alkali  and  run  in  the  acid  cautiously  until 
the  red  color  just  disappears.    Notice  the  volume  of  acid 
used.    One  liter  of  the  acid  contains  36.5  g.  of  hydrogen 
chloride. 

Calculate  the  weight  of  potassium  hydroxide  per  liter, 
which  your  measurement  shows  to  be  contained  in  the  alka- 
line solution  made  in  1  (?).  Express  this  also  in  terms  of  a 
normal  solution  containing  56  g.  per  liter  (for  example,  28  g. 
per  liter  would  be  .5  normal). 

c.  Reactions  of  OH  ions.     Place  very  small  quantities  of 
the  following  solutions  in  separate  test-tubes,  dilute  with 
water,  and  add  some  of  the  solution  of  potassium  hydroxide 
to  each;  ferric  chloride  (?);   cupric  sulphate  (?);  mercuric 
chloride  (?)  [R].     Boil  the  contents  of  each  test-tube  (?). 

What  kind  of  hydroxides  can  be  made  by  this  method? 
Do  any  metals  fail  entirely  to  form  hydroxides  [R]? 

2.  PREPARATION  OF  POTASSIUM  NITRATE.     Dissolve  25  g.  of 
sodium  nitrate  and  22  g.  of  potassium  chloride  in  50  c.c.  of 

83 


84  METALS    OF    THE    ALKALIES 

water  and  evaporate  to  half  the  volume  on  the1  sand-bath. 
Decant  the  hot,  clear  liquid  from  the  crystals  and  set  it  aside. 
Throw  the  crystals  which  appeared  during  boiling-  at  once 
onto  a  filter  (p.  31,  note)  and  rapidly  press  out  the  rest  of  the 
mother  liquor  with  a  spatula.  Examine  the  form  of  the 
crystals  and  ascertain  what  they  are.  (If  they  are  too  small, 
recrystallize  a  part  slowly  from  water  in  a  beaker  in  order  to 
learn  their  form.)  When  the  decanted  liquid  is  cold,  press 
the  product  on  a  filter  likewise.  Examine  this  set  of  crystals 
as  before.  [R.  cf.  figures  in  Roscoe  and  Schorlemmer.]  Com- 
pare both  with  the  original  substances. 

To  understand  the  process  study  the  solubilities  of  the 
substances  concerned  as  they  appear  in  the  following  table: 

Grams  in  10  c.c.  of  water 
10°  100° 

Potassium  nitrate  2.1  24.6 

Sodium  chloride  3.6  4.0 

Potassium  chloride  3.1  5.6 

Sodium  nitrate  8.1  18.0 

Which  of  these  substances  will  first  be  deposited  from  the 
boiling  liquid?  Ascertain  by  calculation  how  much  of  it 
(roughly)  will  be  deposited  at  100°,  how  much  more  will  come 
out  when  the  liquid  cools,  and  how  much  will  remain  in  the 
mother  liquor.  What  other  substance  will  be  present  in 
large  quantity  in  the  hot  mother  liquor,  and  how  much  of  it 
must  there  be  ?  How  much  of  this  product  will  be  deposited 
when  the  liquid  cools,  and  how  much  will  be  lost  by  remain- 
ing dissolved?  What  per  cent  of  the  possible  yield  may  we 
expect  to  get?  Dry  your  product,  weigh  it  and  calculate 
what  per  cent,  was  obtained. 

Explain  why  purer  potassium  nitrate  can  be  obtained  by 
crystallizing  the  product  once  more  from  water.  Whence  the 
necessity  for  making  the  salt  commercially  by  this  method 
at  all  [R]? 

3.  POTASSIUM  CYANIDE  [POISON].  How  is  this  salt  obtained? 
Place  2  c.c.  of  potassium  cyanide  solution  in  an  evaporating 
dish,  heat  it,  and  add  yellow  ammonium  sulphide  solution 
until  the  color  no  longer  disappears.  Evaporate  to  complete 
dryness  [Hood].  Dissolve  a  part  of  the  residue  with  water, 
and  add  ferric  chloride  solution  ( ?).  A  black  precipitate  ( ?) 
indicates  that  the  heating  was  not  sufficient.  If  this  appears, 
heat  the  remainder  once  more  and  try  the  action  of  ferric 
chloride  again.  What  property  of  the  cyanides  does  the 
first  part  of  this  experiment  illustrate  [R]? 


METALS   OF    THE    ALKALIES  85 

4    REACTIONS  OF  POTASSIUM  SALTS. 

a.  Heat  a  little  solid  potassium  nitrate  on  a  clean  platinum 
wire.    Notice  the  color  of  the  flame  and  examine  with  the 
spectroscope.     Make  a  diagram  showing  the  position  of  the 
lines  with  reference  to  the  D  line,  which,  on  account  of  the 
sodium  present,  is  shown  by  all  flames  in  the  laboratory. 

b.  Add  a  strong  solution  of  the  nitrate  (made  by  warm- 
ing), to  tartaric  acid  solution.     Shake  the  mixture  and  cool 
in  a  stream  of  water  (?)    Note,  also,  the  effect  of  rubbing  the 
inside  of  the  test-tube  with  a  glass  rod.     Describe  the  prod- 
uct.    Filter,  press  out  the  mother  liquor,  and  wash  the  pre- 
cipitate with  a  little  alcohol  (see   note).     Dry  by  pressing 
between  filter  papers.    The  nature  of  the  product  (?)  may  be 
inferred  from  the  results  of  c  and  d. 

c.  Dissolve  a  little  of  the  precipitate  in  warm  water  and 
test  its  reaction  with  litmus  paper. 

d.  Place  half  the  remainder  in  a  test-tube  and  add  sodium 
carbonate  solution  a  drop  at  a  time,  mixing  thoroughly,  and 
noticing  all  that  happens  ( ?)     If  any  change  is  observed,  let 
the  action  go  on  until  it  is  complete.    Can  you  explain  why 
evidence  of  the  beginning  of  the  action  is  so  slow  in  making 
its  appearance? 

Add  concentrated  hydrochloric  acid,  a  drop  at  a  time,  to 
the  resulting  solution  (?).  Stir  vigorously  with  a  glass  rod 
at  intervals.  Finally  try  the  effect  of  an  excess  of  hydro- 
chloric acid  (?) 

e.  Heat  the  rest  of  the  precipitate  strongly  in  a  porce- 
lain crucible  (?).     Extract  with  hot  water,  filter,  and  add  any 
acid  to  the  filtrate  (?).     The  ignition  of  all  potassium  or 
sodium  salts  of  organic  acids  gives  the  same  result. 

/.  To  potassium  chloride  solution,  add  picric  acid  solu- 
tion (?). 

What  is  shown  to  be  present  in  a  solution  when  we  get 
the  tests  in  b  and/? 

Note, —  Cut  the  filter-paper  to  circular  form  and  use  the 
smallest  that  will  hold  the  precipitate.  In  washing,  first  let  the 
mother  liquor  drain  away  completely,  and  then  cover  the  contents 
of  the  funnel,  including  the  whole  paper  (why?),  completely  with 
the  washing  material. 

5.  SODIUM.  Recall  the  properties  of  the  metal  as  you 
have  met  them  in  previous  exercises.  From  previous  knowl- 
edge compare  its  behavior  with  that  of  zinc  and  copper 
towards  (a)  air;  (b)  water;  (c)  acids.  What  mineral  is  the 
source  of  the  metal  and  all  its  salts  ? 


86  METALS    OF    THE    ALKALIES 

6.  SODIUM  CARBONATE  BY  SOLVAY  PROCESS.    Take  75  c.c.  of 
ammonium  hydroxide  solution,  diluted  with  25  c.c.  of  water, 
dissolve  in  it  25  g.  of  powdered  ammonium  carbonate  by 
shaking,  and  then   saturate   the   solution   completely   with 
sodium  chloride  by  prolonged  agitation  with  finely  powdered 
salt  in  a  corked  bottle.     If  common  salt   is  employed,   it 
should  be  washed  with  water  before  use.     Decant  the  clear 
liquid  into  another  bottle,  fitted  with  cork  and  two  tubes,  one 
of  which  reaches  to  the  bottom.     Through  the  latter,  pass  in 
carbon  dioxide  from  a  Kipp's  apparatus  until  the  solution  is 
saturated.     This  operation   may  occupy  an   hour  or  more. 
During  the  absorption  of  the  carbon  dioxide,  the  exit  tube 
should  be  closed  to  prevent  waste  of  the  gas.     Close  the 
tubes  with  caps  of  rubber  tubing  plugged  with  glass  rods 
[Instructions]  and  set  aside  over  night  (?).     Filter  off   the 
deposit  and  dry  by  pressing  between  filter  papers. 

Dissolve  in  water  a  little  of  the  solid,  which  must  have 
ceased  to  smell  of  ammonia,  and  test  the  reaction  of  the 
solution  with  litmus  ( ?). 

To  part  of  the  solid  add  any  dilute  mineral  acid  (?). 

Heat  the  rest  in  a  test-tube  clamped  so  that  the  mouth 
is  inclined  slightly  downward,  and  ascertain  what  gases  are 
evolved.  When  gas  ceases  to  be  given  off,  dissolve  the  cold 
residue  in  a  very  little  water,  test  the  reaction  of  the  solution 
with  litmus  paper  ( ?),  and  set  it  aside  to  crystallize  in  an 
open  dish  (?).  Ascertain  the  effect  of  exposure  in  an  open 
vessel  (?)  and  the  action  of  acids  (?)  on  the  the  crystals. 

The  solubilities  at  20°  of  the  bicarbonate  and  carbonate 
in  100  parts  of  water  are  9.6  and  92.8  respectively.  Explain 
why  the  bicarbonate  is  made  first  and  then  the  carbonate 
from  it. 

7.  REACTION  OF  SOLUBLE  CARBONATES:    PROPERTIES  OF  CO3 
IONS  (CARBONANION).    Add  sodium  carbonate  solution  to  dilute 
solutions  of  barium  chloride  (?),  lead  nitrate   (?),   chromic 
chloride  (?),  cupric  sulphate  (?).     Add  the  carbonate   cau- 
tiously at  first,  note  the  gas  given  off  in  some  cases  and 
account  for  its  formation.     The  gas  is  often  slow  to  appear 
(why?).     Filter  the  contents  of  each  test-tube  and  wash  each 
precipitate  thoroughly  (cf.  p.  85,  4,  /,  note)  with  water.    What 
are  those  precipitates  ?    Test  your  conclusions  by  a  suitable 
experiment  in  each  case. 

Save  part  of  the  lead  compound  and,  when  it  is  dry,  heat 
it  in  a  dry  test-tube  and  ascertain  what  gas  is  given  off  (?). 
What  carbonates  show  this  behavior  [R]? 

8.  PURIFICATION  OF  SODIUM  CHLORIDE.     Wash  some  crude 
salt  with  water  and  then  prepare  about  150  c.c.  of  cold  sat- 


METALS    OF    THE    ALKALIES  87 

urated  solution  by  grinding  the  salt  for  some  time  in  a  mortar 
with  the  water.  Place  it  in  a  beaker  and  pass  hydrogen 
chloride  into  the  solution.  Prepare  this  gas  by  placing  a 
handful  of  common  salt  in  a  generating  flask,  covering  it  with 
concentrated  hydrochloric  acid  and  allowing  concentrated 
sulphuric  acid  to  fall  into  it  from  a  dropping- funnel.  Deliver 
the  gas  into  the  solution  through  a  thistle  tube  with  the 
mouth  downwards  (why  use  this  tube)?.  When  considerable 
precipitation  has  occurred,  filter  by  putting  a  clean  silver 
coin  in  a  funnel,  pouring  the  liquid  and  crystals  upon  it  and 
pressing  with  a  spatula. 

Explain  why  the  salt  is  precipitated.  If  sodium  sulphate 
or  magnesium  chloride  or  some  other  salt  has  been  mixed 
with  the  salt,  would  they  have  been  thrown  down  [R]?  In 
other  words,  why  does  this  process  give  a  means  of 
purification? 

Explain  the  method  of  generating  hydrogen  chloride 
used  above. 

This  question  may  be  answered  after  the  experiments 
in  9. 

9.  IONIC    EQUILIBRIUM. 

a.  Dilute  a  few  drops   of    methyl  orange  solution  with 
distilled  water.    Add  to  it  first  a  few  drops  of  an  acid  ( ?)  and 
then  a  few  drops  of  a  base  (?). 

Take  three  portions  of  distilled  water  and  add  to  each  a 
little  methyl  orange  solution.  To  the  first  two  add  a  little 
acetic  acid  (?),  to  the  third  a  drop  or  two  of  hydrochloric 
acid  (?).  What  kind  of  ions  is  absent  when  the  indicator  is 
yellow?  Add  some  solid  sodium  chloride  to  the  first  and 
stir  ( ?).  To  the  second  add  solid  sodium  acetate  and  stir  ( ?). 
Explain  the  difference  in  behavior.  To  the  third  add  solid 
sodium  chloride  and  stir  ( ?).  Explain  absence  of  effect. 

b.  Take  three  portions  of  a  saturated  solution  of  potas- 
sium chlorate  in  as  many  test-tubes.     (This  and  the  following 
solutions  must  be  shaken  to  insure  saturation  if  there  is  a 
deposit  in  the  bottles.)    To  the  first  add  saturated  sodium 
chloride   solution   (?),  to    the    second  saturated  potassium 
chloride  solution  (?),  to  the  third  saturated  sodium  chlorate 
solution  ( ?).    Allow  them  to  stand  for  a  minute  or  two  before 
drawing  any  conclusion.     Explain.     The  experiments  will 
fail  if  the  solutions  are  not  saturated. 

10.  REACTIONS  OF  SODIUM  SALTS.     Try  the  flame  test  and 
examine  with  the  spectroscope  (?).     Add  tartaric  acid  (?)  and 
picric  acid  ( ?)  solutions  to  separate  portions  of  diluted  sodium 
chloride  solution.    Compare  with  results  under  potassium. 


88  METALS    OF    THE    ALKALIES 

11.  AMMONIUM  SALTS.  What  is  the  effect  of  heating  am- 
monium salts  (p.  36,  4,  d)?  Heat  some  ammonium  phosphate 
in  a  hard  glass  test-tube  ( ?).  Dissolve  the  residue  in  water 
and  test  with  litmus  paper.  Heating  and  searching  for  an 
odor  of  ammonia  is  not  a  sure  test  for  ammonium  salts.  In 
many  cases  the  odor  would  not  be  perceived. 

Try  the  flame  test  with  an  ammonium  salt  (?). 

To  two  portions  of  ammonium  chloride  solution  add 
excess  of  tartaric  acid  solution  (?)  and  picric  acid  solution  (?) 
respectively.  What  other  ion  gives  the  same  results  as 
ammonium  with  these  reagents  ?  To  a  third  portion  add  a 
strong  base  and  warm  ( ?).  Notice  the  odor.  This  is  the  best 
test  for  ammonium  salts.  How  could  you  distinguish  between 
solutions  containing  ammonium  and  potassium  salts  ? 

Make  a  list  of  the  salts  of  potassium,  sodium,  and  ammon- 
ium which  are  least  soluble  [R  and  exps.]. 


CHAPTER  XX. 

METALS  OF  THE  ALKALINE  EARTHS, 

1.  Heat  2-3  g.  of  powdered  marble  for  fifteen  minutes  in 
an  open  porcelain  crucible,  with  a  blast-lamp  (?).  Add  a 
little  water  to  the  product  when  it  has  cooled  (?).  (Has  water 
any  effect  on  marble?)  Test  the  reaction  of  the  liquid  with 
litmus.  What  was  formed  by  heating  marble?  The  action 
is  reversible.  (How  is  this  suggested  by  the  behavior  of 
mortar?)  On  what  will  the  re-formation  of  marble  depend 
at  any  given  temperature  [R]? 

2.  LIME  WATER.     Slake  a  small  piece  of  calcium  oxide  and 
shake  the  product  with  half  a  liter  of  distilled  water,  let  the 
solution  settle,  and  use  the  clear  liquid. 

a.  Blow  air  from  the  lungs  by  means  of  a  tube  through 
a  part  of  the  lime  water  (?).  How  could  you  determine  the 
proportion  of  carbon  dioxide  in  a  sample  of  air? 

6.  Pass  carbon  dioxide  from  a  Kipp's  apparatus  persist- 
ently through  the  remainder  of  the  lime  water  (?).  Boil  a 
part  of  the  resulting  clear  solution  (?).  Explain  [R]. 

3.  REACTIONS   OF  CALCIUM   SALTS.     Use   calcium   chloride 
solution  and  dilute  it  for  6,  c,  and  d.    [In  this  and  all  follow- 
ing paragraphs  headed  "  reactions,"  where  diluted  solutions 
are  spoken  of,  the  strong  solutions  on  the  side-shelf  must  be 
diluted  with  three  to  four  times  their  volume  of   water  to 
secure  good  results.] 

a.  Try  the  flame  test  and  examine  with  the  spectroscope 
(see  that  the  platinum  wire  is  clean).     Make  a  sketch  of  the 
spectrum  showing  the  positions  of  the  lines  with  reference  to 
the  sodium  and  potassium  lines. 

b.  To  a  solution  containing  calcium  ions  add  ammonium 
carbonate  solution,  and  warm  if  necessary. 

c.  To  another  portion  of    the   solution  add  oxalic  acid 
solution  (?).     [Formation  of  all  precipitates,  if  long  delayed, 
may  be  hastened  by  vigorous  stirring  with  a  glass  rod.] 

d.  To  another   portion    add  excess  of   dilute   sulphuric 


90        METALS  OF  THE  ALKALINE  EARTHS 

acid  (?).  Filter,  and  neutralize  the  filtrate  roughly  with 
ammonium  hydroxide.  To  this  solution  add  ammonium 
oxalate  solution  (?),  and  explain  (p.  28,  7,  d  and  p.  52,  7,  a). 
Is  the  sulphate  or  oxalate  of  calcium  more  soluble  ? 

4.  REACTION  OF  STRONTIUM  SALTS.     Use  strontium  chloride 
solution  and  dilute  it  for  b  and  c. 

a,  b.  Same  as  in  3. 

c.  To  a  portion  of  the  strontium  chloride  solution  add  a 
solution  of  calcium  sulphate  ( ?)  made  by  shaking  a  little  of 
the  powdered  salt  with  water  and  decanting,  and  explain. 
The  precipitation  may  be  very  slow. 

5.  REACTIONS  OF  BARIUM  SALTS.     Use  barium  chloride  solu- 
tion and  dilute  it  for  6,  and  c. 

a,  b.  Same  as  in  3  and  4. 

c.  To  a  portion  of  the  solution  of  barium  chloride  add  a 
solution  of  strontium  sulphate  ( ?)  made  by  shaking  the  salt 
with  water  and  decanting,  and  explain. 

Arrange  the  sulphates  of  these  three  metals  in  order  of 
solubility.  How  could  you  tell  a  solution  containing  the  ions 
of  a  member  of  this  family  from  one  containing  those  of  the 
previous  family? 

Give  two  methods  of  distinguishing  between  the  members 
of  the  present  group. 

6.  INSOLUBLE  SULPHATES.     To  a  little  lead  nitrate  solution 
add  dilute   sulphuric  acid(?).     Which  sulphates   have   you 
found  to  be  insoluble?     These  complete  the  list,  as  far  as 
common  metals  are  concerned. 

7.  Take  three  dry  test-tubes,  apply  to  the  instructor  for 
three  "  unknown  "  substances,  and  ascertain  what  each  is,  by 
the  use  of  any  experiments  you  can  devise. 

SUGGESTIONS.     Study: 

(1)  Physical  appearance  (?). 

(2)  Odor(?). 

(3)  Solubility  in  water  and  reaction  of  the  solution  toward 
litmus  (?). 

(4)  Effect  of  heating  in  a  dry  test-tube  (?).    Save  the  resi- 
due, as,  after  next  experiment,  examination  of  this  may  be 
necessary. 

(5)  Effect  of  heating  with  concentrated  sulphuric  acid  (?). 
Before  trying  the  last  two  tests,  make  a  list  of  all  the 

gases  which  may  be  expected,  the  means  of  identifying  each, 


METALS    OF    THE    ALKALINE    EABTHS  91 

and  the  corresponding  inferences  with  regard  to  the 
unknown  substance.  Test  gases  given  off  according  to  cir- 
cumstances. The  result  of  these  experiments  will  suggest 
further  work.  The  metals  may  be  identified  by  the  reactions 
given  in  Chaps.  XIX  and  XX. 

Make  sure  that  your  experiments  and  reasoning,  which 
should  be  carefully  written  out,  prove  that  the  substance  is 
the  one  you  finally  decide  that  it  is.  and  exclude  the  possibil- 
ity of  it  being  any  other.  Report  the  result  to  the  instructor. 


CHAPTEK  XXI. 

COPPER    AND    SILVER. 

1.  CUPROUS  CHLORIDE  [Hood].     Dissolve  about  5  g.  of  cop- 
per clippings  in  warm  aqua  regia,  using  the  minimum  of 
nitric  acid  that  will  effect  the  solution  of  the  metal.     Why  is 
the  nitric  acid  required,  and  what  other  substances  might 
serve  the  same  purpose  ?     Evaporate  to  dryness  on  the  steam 
bath  [Hood]  and  re-dissolve  in  25  c.c.  of  water.     Transfer  to 
a  flask,  add  an  equal  volume  of  concentrated  hydrochloric 
acid  and  about  10  g.  of  copper  clippings  and  boil  [Hood] 
gently  until  the  green  tint  is  no  longer  perceptible  in  the 
dirty  yellowish-brown  color  of  the  product  ( ? ).     If  a  few  drops 
added  to  a  test-tube  full  of  water  confer  a  blue  tinge  on  the 
solution  the  action  is  still  incomplete. 

To  a  small  part  of  this  solution,  when  cold,  add  sodium 
hydroxide  solution  (?).  Why  is  so  much  of  this  required? 
Divide  the  mixture  into  two  parts.  Notice  whether  the  pre- 
cipitate undergoes  any  change  on  shaking  with  air  (?).  For 
comparison,  add  sodium  hydroxide  solution  to  cupric  sulphate 
solution  (?).  Explain.  Heat  the  other  half  (?). 

Pour  the  rest  of  the  cuprous  chloride  solution  into  a  large 
amount  of  water  in  a  beaker  (?).  Expose  some  of  the  sub- 
stance while  covered  with  water  to  the  sunlight  ( ?).  What 
properties  of  cuprous  chloride  have  you  observed? 

2.  DOUBLE  SALTS. 

a.  Saturate   water  at  70°   with  5  g.  of  finely  powdered 
potassium  sulphate  (about  25  c.c.  will  be  required).     Calcu- 
late the  weight  of  crystallized  cupric  sulphate  which  must  be 
taken  to  get  an  equi-molecular  proportion,  and  dissolve  it  in 
its  own  weight  of  hot  water.     Mix  the  two  solutions,  taking 
care  not  to  allow  any  undissolved  fragments  of  either  salt  to 
get  into  the  mixture,  and  set  the  result  aside  to  crystallize  ( ?). 
Examine  the  form  of  the  crystals  and  compare  with  those  of 
blue  vitriol  (?).     Keep  them  for  use  later. 

b.  To  a  little   cupric   sulphate  solution  add  potassium 
cyanide  solution  till  no  further  change  occurs  ( ?)  [B],     Keep 
this  solution. 

After  applying  to  these  two  preparations  the  tests  in  4,  c 


COPPER    AND    SILVER  93 

and  d,  state  the  nature  of  the  difference  between  the  two 
bodies  here  examined. 

3.  EQUIVALENT  OF  COPPER  [Quant.].    Take  a  small  rod  of 
pure  zinc,  smooth  ends  with  a  file  and  weigh  carefully.  Place 
in  a  beaker  an  exactly  known  weight  of  crystallized  cupric 
sulphate  (about  2  g.),  and  dissolve  in  distilled  water.     Put 
the  zinc  in  this  solution  and  allow  them  to  remain  in  contact 
until  the  latter  is  completely  decolorized.    Remove  the  zinc, 
free  it  carefully  from  the  brown  deposit  ( ?),  and  dry  and  weigh 
it.     What  weight  of  zinc  has  gone  into  solution? 

To  avoid  weighing  the  precipitate  of  copper,  which  it 
would  be  difficult  to  do  exactly,  calculate  from  the  formula  what 
quantity  of  copper  was  contained  in  the  amount  of  blue  vitriol 
taken  (?).  Calculate  the  equivalent  weight  of  copper  (that  of 
oxygen  being  8),  using  the  value  for  the  equivalent  of  the  zinc 
found  in  Chap.  V,  2,  6  or  3,  a  (p.  17)  or,  if  zinc  was  not  then 
employed,  assume  it  to  be  32.7.  Look  up  the  specific  heat  of 
copper  (p.  20)  and  find  its  atomic  weight  from  the  equivalent 
observed. 

What  other  atomic  weights  could  be  measured  on  this 
plan? 

4.  REACTIONS  OF  CUPRIC  SALTS.  Use  diluted  cupric  sulphate 
solution.     What  is  the  color  of  cupric  sulphate  itself?     To 
what  is  the  color  of  the  solution  due  ? 

a.  Test  the  reaction  of  the  solution  with  neutral  litmus 
paper  (?)  and  explain. 

b.  Add    ammonium    hydroxide  till    no  further  change 
occurs  (?).    This  is  used  as  a  test  for  salts  of  copper. 

c.  Pass  hydrogen  sulphide  gas  through  another  portion. 
Make  a  solution  of  part  of  the  crystals   in  2,  «,  and  apply 
this  test  to  it  (?)  and  to  a  part  of  the  solution  from  2,  b  (?). 

d.  Same  as  c,  using  potassium  ferrocyanide  solution  in 
place  of  hydrogen  sulphide.     Answer  the  question  at  the 
end  of  2. 

e.  Add  potassium  iodide  solution  to  a  fresh  portion  (?). 
Filter,  wash  the  precipitate  ( ?),  and  add  a  drop  of  the  filtrate 
to  starch  emulsion  (?). 

/.  Make  a  borax  bead  and  heat  it  with  a  minute  particle 
of  cupric  oxide  in  the  oxidizing  (?)  and  in  the  reducing  (?) 
flame.  The  latter  requires  patience. 

g.  Try  the  match  test  (p.  74,  14)  with  any  copper  com- 
pound. 

h.  Boil  a  little  of  a  dilute  sugar  solution  with  a  few  drops 


COPPER    AND    SILVER 

of  sulphuric  acid  for  a  minute  or  two.  Add  cupric  sulphate 
solution  and  excess  of  sodium  hydroxide  solution  and  warm 
(cf.  1)  [B]. 

5.  REACTIONS  OF  SILVER  SALTS. 

a.  Take  some  silver  nitrate  solution  and  add  to  it  dilute 
hydrochloric  acid  till  no  further  precipitation  occurs.     Filter 
and  wash  with  water. 

What  effect  does  the  skin  have  on  silver  nitrate  ? 

b.  Treat  part  of  the  precipitate  with  ammonium  hydrox- 
ide (?).     Then  add  dilute  nitric  acid  to  the  solution  (?). 

c.  Place  the  rest  of  the  precipitate  in  a  porcelain  crucible, 
put  on  it  a  piece  of  granulated  zinc,  and  fill  up  with  dilute 
sulphuric  acid.     Stir  from  time  to  time  (?).     After  an  hour  or 
two  pour  off  the  acid,  take  out  any  unchanged  zinc,  wash  the 
precipitate  with  water  by  decantation,  add  ammonium  hydrox- 
ide, and  filter.     Find  out  whether  there  is  any  silver  chloride 
in  the  filtrate  (?,  cf.  6).     When  the  filter  paper  is  dry,  place  the 
dark  powder  in  a  hollow  on  a  stick  of  charcoal  and  melt  it  with 
the  flame  of  the  blast-lamp  directed  downward  upon  it  ( ?). 

d.  To  a  little  silver  nitrate  solution  add  some  potassium 
dichromate  solution  (?).     Test  the  solutions  before  and  after 
mixing,  with  neutral  litmus  paper (?).     [If  the  color  of  the 
dichromate  obscures  that  of  the  litmus,  wash  the  test-paper 
with  distilled  water.] 

6.  THE  PROPERTIES  OF  A  METALLIC  ELEMENT.     The  proper- 
ties of  a  metal,  in  the  chemical  sense  of  the  word,  are:  (1) 
The  element  may  be  the  sole  constituent  of  a  cation  (positive 
ion).      (2)  Its  hydroxyl  compound  is  a  base.      (3)  Its  salts 
should  not  be  hydrolyzed  by  water. 

Do  copper  and  silver  completely  fulfil  these  conditions? 
If  not,  in  what  respects  do  they  fail  to  do  so? 


CHAPTER   XXII. 

MAGNESIUM,  ZINC,  CADMIUM,  MERCURY. 

1.  PROPERTIES  OF  MAGNESIUM  COMPOUNDS. 

a.  Try  whether  magnesium  chloride  dissolves  completely 
in  water  (?).     Test  the  solution  with  litmus  (?). 

Heat  some  of  the  crystals  strongly  in  a  dry  test-tube  (?). 
Test  the  reaction  towards  litmus  paper  of  the  water  which 
condenses  in  the  tube(?),  and  then  remove  the  liquid  from 
the  sides  of  the  tube  with  a  piece  of  filter  paper.  Does  the 
residue  dissolve  in  water?  Explain. 

b.  To   some   diluted  magnesium  sulphate   solution  add 
ammonium  hydroxide  ( ?).     Explain  the  result  in  terms  of  the 
theory  of  ionization.     Now  mix  with  some  ammonium  hydrox- 
ide several  times  its  volume  of  ammonium  chloride  solution 
(what  effect  will  this  have  on  the  ionization  of  ammonium 
hydroxide?)  and  then  add  the  mixture  to  a  fresh  portion  of 
the  magnesium  sulphate  solution  ( ?).     Explain.     To  this  com- 
bination of  three  solutions  add  sodium  phosphate  solution  (?) 
[R].     Write  the  equation  and  explain  the  purpose  for  which 
each  ingredient  was  used. 

c.  To  a  fresh  portion  of  the  diluted  magnesium  sulphate 
solution   add  ammonium   carbonate  solution  and  warm(?). 
What  other  metal  ions  were  precipitated  by  the  same  reagent  ? 
Repeat,  adding  excess  of  ammonium  chloride  solution  to  the 
magnesium  sulphate  solution  before  using  the  carbonate  (?). 
Try  whether,  with  this  modification,  the  salts  of  those  other 
metals  still  behave  like  those  of  magnesium.     If  you  had  a 
salt  of  magnesium  mixed  with  a  salt  of  one  of  those  other 
metals,  how  would  you  proceed  so  as  to  precipitate  a  com- 
pound of  the  alkaline  earth  metal  first  and  one  of  magnesium 
afterwards?     Explain  the  effect  of  the  ammonium  chloride 
as  in  b. 

Add  two  drops  of  hydrochloric  acid  (why  ?)  to  about  250 
c.c.  of  the  city  water,  evaporate  to  small  bulk,  and  test  it  for 
calcium  and  magnesium. 

d.  Pass  hydrogen  sulphide  through  some  magnesium  sul- 
phate solution  (?). 

2.  SALTS  OF  ZINC.     Use  diluted  zinc  sulphate  solution  for 
6,  c,  and  d. 

95 


96  MAGNESIUM,  ZINC,  CADMIUM,  MERCURY 

a.  Relative  activity  of  acids.     In  three  clean  test-tubes 
place  (1)  zinc  chloride,  (2)  zinc  sulphate,  and  (3)  zinc  acetate 
solutions.     Test  each  with  litmus  paper  (?).     Pass  hydrogen 
sulphide    to    saturation    (test  I)   through   each    solution  ( ?). 
Filter  the  mixtures  separately,  test  the  reaction  of  each  nitrate 
with   litmus   paper  (?),   and  add    ammonium    hydroxide   to 
each(?).     In  considering  the  nature  of  the  product  produced 
by  the  last  reagent,  remember  that  the  water  is  saturated  with 
hydrogen  sulphide,  and  that  therefore  ammonium  sulphide  is 
formed  in  it. 

How  do  the  three  salts  differ  in  behavior?  How  do  you 
account  for  this  difference?  In  answering  this  question  it  will 
be  found  helpful  to  scrape  a  little  of  the  precipitate  into  each 
of  two  test-tubes  and  to  treat  one  with  diluted  hydrochloric 
acid  (?)  and  the  other  with  diluted  sulphuric  acid(?).  What 
evidence  is  there  that  the  actions  are  reversible?  Which 
shows  this  most  markedly  and  which  least  so?  Can  you 
infer  from  this  the  relative  activities  of  the  three  acids? 
Preserve  some  of  the  precipitate  for  use  in  d. 

b.  Ionic  equilibrium.     Take  a  larger  amount  of  zinc  sul- 
phate solution  and  add  sulphuric  acid  to  it  cautiously  until 
a  sample  ceases  to  give  any  precipitate  with  hydrogen  sul- 
phide.    Explain.     Now  add  much  powrdered  solid  sodium 
sulphate,  stir  until  it  has  dissolved,  and  test  a  part  with 
hydrogen  sulphide  again.     Explain.     Write  this  equation  so 
as  to  show  that  the  action  is  reversible  and  that  an  equilib- 
rium exists. 

c.  To  zinc  sulphate  solution  add  caustic  soda  solution 
until  no  further  change  occurs  (?).     Explain  [R]. 

d.  Take  a  piece  of  filter  paper  from  a  with  a  very  little 
zinc  sulphide  on  it,  roll  it  up,  and  twist  the  platinum  wire 
tightly  round  it.      Roast  the  whole  in   the  Bunsen  flame. 
Moisten    the    ash  with   cobalt  chloride   solution   and  heat 
again  (?). 

3.  CADMIUM  SALTS.    Take  two  samples  of  a  diluted  solution 
of  any  cadmium  salt.      Test  the.  reaction  with  litmus.     To 
the  first  add  hydrogen   sulphide  gas  (?).      To  the   second 
add  sodium  hydroxide  solution   in  excess  (?).     Acidify  the 
result  of  the  first  with  hydrochloric  acid  (?).     How  do  the 
salts  of  this  metal  differ  in  behavior  from. those  of  zinc? 

By  what  reactions  could  you  distinguish  between  salts  of 
magnesium,  zinc,  and  cadmium  ? 

4.  Apply  to  the  instructor  for  three  unknown  substances 
and  identify  them. 


MAGNESIUM,  ZINC,  CADMIUM,  MERCURY  97 

5.  MERCUROUS  NITRATE.    Place  about  10  g.  of    mercury 
with  15  c.c.  of  diluted  (1 :1)  nitric  acid  in  a  small  beaker  and 
let  the  action  go  on  for  an  hour  or  two,  or  until  fresh  crystals 
cease  to  be  formed.      If  crystallization  is  long  in  starting, 
stirring,  or  infection  with  a  crystal  of  mercurous  nitrate  will 
bring  it  about.    Pour  away  the  liquid    and  dissolve  the 
crystals  in  water  to  which  a  few  drops  of   nitric  acid  have 
been  added  (why?).    This  solution,  if  ready,  may  be  used 
in  6. 

How  could  you  make  mercuric  nitrate  solution? 

6.  REACTIONS  OF  SALTS  OF  MERCURY.     Use  diluted  portions 
of    mercurous   nitrate  solution   and  of    a  solution  of    any 
mercuric  salt  and  add  to  each  the  following  reagents.    Com- 
pare results  in  each  case. 

a.  Litmus  (?). 

b.  Dilute  hydrochloric  acid  (?).    Treat  the  precipitate,  if 
there  is  any,  with  ammonium  hydroxide  ( ?)  [R] 

c.  Hydrogen  sulphide  to  saturation  (?),  then  acidify  (?). 

d.  Ammonium  hydroxide  (?)  [R] 

e.  Sodium  hydroxide  (?). 

/.  Potassium  iodide  till  there  is  no  further  change  ( ?). 

g.  Stannous  chloride  till  there  is  no  further  change  (?). 

h.  Clean  copper  clippings  ( ?).  Ascertain  experimentally 
whether  any  copper  goes  into  solution  ( ?). 

i.  Heat  any  salt  of  mercury  strongly  in  a  narrow  tube 
closed  at  one  end  ( ?). 

How  could  you  distinguish  a  solution  of  a  mercurous  and 
of  a  mercuric  salt,  respectively,  from  salts  of  silver,  bismuth, 
magnesium,  zinc,  and  cadmium  ? 

7.  Do  these  four  metals  exhibit  the  properties  of  metallic 
elements  (p.  94,  6)?     If  not,  in  what  respects  do  they  fail  to 
do  so? 


CHAPTER  XXIII. 

ALUMINIUM,  TIN,  LEAD. 

1.  ALUMINIUM. 

a.  Recall  the  effect  of   hydrochloric  acid  on  aluminium 
(p.  22,  1,  a)  (?).     Try  diluted  nitric  acid  (?). 

b.  Heat  a  piece  of  aluminium  wire  with  sodium  hydrox- 
ide  solution  for  some   minutes  (?).     To  ascertain  whether 
anything  has  gone  into  solution,  neutralize  carefully  with 
dilute  hydrochloric  acid(?).      Neutralize  a  sample  of   the 
caustic  soda  solution  employed  ( ?).     If  there  is  a  precipitate 
in  either  case  test  it  by  3,  e. 

2.  ALUM.    Prepare  warm  saturated  solutions  of  anhydrous 
aluminium    sulphate   and  ammonium   sulphate  in  approxi- 
mately equi-molecular  proportions,  mix  them,  and  set  aside  ( I). 
Obtain   some   large   crystals   by  hanging  a   thread   in   the 
solution.     Notice  the  form  of  the  crystals. 

Ascertain  by  experiments  selected  from  3  whether  a  solu- 
tion of  this  salt  behaves,  in  respect  to  the  aluminium  which 
it  contains,  like  a  mixture  of  the  constituent  salts  or  like 
a  different  salt  Is  alum  a  double  salt  or  a  salt  of  a  complex 
acid? 

3.  REACTIONS   OF  ALUMINIUM   COMPOUNDS.     Use   a   diluted 
aluminium  sulphate  solution. 

a.  Test  the  solution  with  litmus  ( ?). 

b.  Add  sodium  carbonate  solution  (?).     Isolate  the  pre- 
cipitate and  find  out  whether  it  is  a  carbonate  or  not. 

c.  To  another  portion    add    colorless    ammonium    sul- 
phide ( ?).     Find  out  experimentally  whether  the  precipitate 
is  a  sulphide  or  not  ( ?).     Preserve  part  of  the  precipitate  for 
use  in  e. 

d.  To  another  portion  add  sodium  hydroxide   solution 
gradually  (?).      Filter,  suspend  part   of   the  precipitate  in 
water,  and  treat  with  more  sodium  hydroxide  solution  (?). 
What  other  hydroxide  behaves  like  this  ?     Treat  another  part 
of  the  precipitate  similarly  with  hydrochloric  acid  (?).   What 
peculiarities  does  this  hydroxide  show? 

e.  Wrap  up  part  of  the  filter  paper  from  c,  twist  the  plat- 


ALUMINIUM,  TIN,  LEAD  99 

inum  wire  tightly  round  it,  char  in  the  Bunsen  flame,  moisten 
with  cobalt  chloride  solution,  and  heat  again  ( ?). 

/.  To  some  cochineal  solution  add  any  solution  contain- 
ing aluminium  sulphate  and  then  ammonium  hydroxide  ( ?). 
Filter.  Repeat  the  treatment  with  aluminium  sulphate  and 
ammonium  hydroxide,  if  necessary  (?). 

4.  HALIDES  OF  TIN. 

a.  Stannous  chloride.    Dissolve  tin  in  warm  concentrated 
hydrochloric  acid.    Let  the  action  go  on  until  the  acid  is 
nearly  exhausted.    Use  the  solution  in  4,  6,  and  5.    Proceed 
with  6,  8,  and  9  until  it  is  ready. 

b.  Stannic  halide  [Hood].    To  part  of  the  solution  from 
a  add  bromine  until  the  color  ceases  to  be  destroyed  and  drive 
off  the  excess  of  bromine  by  warming  (?).    Use  this  liquid 
in  5. 

5.  -REACTIONS  OF  STANNOUS  AND  STANNIC    SALTS.     Use  a 
portion  of  each  of  the  above  solutions,  after  diluting  as 
usual,  with  each  reagent. 

a.  Saturate  (test  ?)  each  solution  with  hydrogen  sulphide 
(!).    Neutralize  with  ammonium  hydroxide  and  add  yellow 
ammonium  sulphide  to  each  product  ( ?).    Filter  and  acidify 
each  resulting  solution  with  hydrochloric  acid  ( ?). 

b.  Add  mercuric  chloride  solution  to  fresh  portions  of 
each  ( ?).    Boil  a  portion  of  the  stannic  halide  with  a  piece  of 
tin  for  a  minute  or  two  and  test  with  mercuric  chloride  solu- 
tion again  (?). 

c.  Add  sodium    hydroxide  solution  to    each    until    no 
further    change    occurs    (?).      What    peculiarity    do    these 
hydroxides  exhibit  ? 

6.  SOLUTION  TENSION  AND  ION  CONCENTRATION.     Suspend  a 
rod  of  tin  about  60  mm.  long  by  a  thread  from  one  end,  and 
hang  it  near  the  bottom  of  a  wide  test-tube  or  narrow  cylin- 
der.   Pour  in  through  the  dropping  funnel,  which  must  reach 
the  bottom  of  the  cylinder,  first  highly  diluted  dilute  hydro- 
chloric acid  (1 : 3)  and  then  diluted  (1 : 1)  stannous  chloride 
solution.    Perform  the  operation  with  care,  in  such  a  way 
that  the  solutions  do  not  mix  and  that  the  surface  at  which 
they  meet  is  near  the  middle  of  the  rod  of  tin.     If  the  second 
solution  is  permitted  to  carry  air  bubbles  with  it,  mixing  will 
inevitably  occur.    Place  the  arrangement  where  it  will  not 
be  disturbed,  and  examine  it  from  time  to  time  (?).     Explain 
[B]. 

7.  Apply  to  the  instructor  for  two  unknown  substances 
and  identify  them. 


100  ALUMINIUM,  TIN,  LEAD 

8.  LEAD. 

a.  Dissolve  1  g.  of  lead  acetate  in  20  c.c.  of  water,  place 
in  it  several  pieces  of  granulated  zinc  and  let  them  remain 
for  an  hour  or  two.     Preserve  the  solution  and,  after  9,  devise 
a  way  of  precipitating  any  remaining  ionic  lead  and  showing 
the  presence  of  zinc  in  the  solution,  and  see  whether  it  works. 

b.  Wash  some  of  the  lead  from  a  with  distilled  water  and 
see  whether  it  is  possible  to  get  washings  which  show  no 
reaction  with  hydrogen  sulphide  ( !).    Account  for  what  you 
observe. 

9.  REACTIONS  OF  LEAD  SALTS.     Use  diluted  lead  nitrate 
solution. 

a.  Test  the  solution  with  litmus  (?). 

b.  Hydrogen  sulphide  ( ?). 

c.  Hydrochloric  acid  (?).    Filter,  dilute  the  nitrate,  and 
pass    hydrogen    sulphide  through  it  (?).    Explain.     What 
other  chlorides  are  more  or  less  insoluble  in  water  ? 

d.  Potassium  iodide  solution  ( ?).    Boil  the  result,  filter, 
and  examine  the  filtrate  (?).     What  property  of  plumbic 
iodide  is  indicated? 

e.  Add  sodium  hydroxide    gradually  (?)  and  then    in 
excess  (?).     Compare  the  behavior  of  the  hydroxide  with  that 
of  hydroxides  of  zinc,  aluminium,  and  tin. 

/.  Potassium  dichromate  solution  (?).  Test  the  solutions 
with  litmus  paper  before  and  after  mixing  (?).  The  result 
will  throw  light  on  the  nature  of  the  action  [R]. 

Does  lead  form  any  compounds  in  which  it  is  quadriva- 
lent [R]? 

Explain  the  action  of  minium  on  hydrochloric  acid  (p.  30, 
1,  a). 

10.  Do  these  three  metals  exhibit  the  properties  of  metal- 
lic elements  (p.  94  Q)f     If  not,  in  what  respects  do  they  fail 
to  do  so? 


CHAPTER    XXIV. 

CHROMIUM,    MANGANESE. 

1.  CHROMIC  OXIDE.  Mix  some  potassium  dichromate  (15  g.) 
thoroughly  with  one-fifth  its  weight  of  powdered  sulphur 
and  heat  with  the  blast-lamp  in  a  porcelain  crucible  for  fif- 
teen minutes.     Grind  up  the  resulting  mass  in  a  mortar  with 
water,  filter,  wash  the  green  residue  ( ?),  and  dry  it  on  a  radia- 
tor for  use  in  2. 

Make  a  borax  bead,  dissolve  a  particle  of  chromic  oxide 
in  it,  and  note  the  effects  of  the  oxidizing  and  reducing 
flames  on  it  ( ?).  All  chromium  compounds  give  the  same 
result.  If  chromic  sulphate  had  been  used,  what  would  have 
been  the  nature  of  the  chemical  action  ? 

2.  CHROMIC  CHLORIDE.     Mix  the  chromic  oxide  prepared 
in  1  with  one-third  its  weight  of  powdered  wood  charcoal, 
make  into  a  stiff  paste  with  some  starch,  and  mold  the  mix- 
ture into  little  pellets  of  the  size  of  peas.     Cover  these  com- 
pletely with  a  layer  of  charcoal  powder  (why  ?)  in  a  closed 
crucible,  dry  them  by  heating  with  the  Bunsen  flame  and  let 
them  cool  before  exposing  them  to  the  air  (why  ?).    Place  them 
in  a  piece  of  hard  glass  tubing.     Then  connect  with  a  chlor- 
ine apparatus  and,  when  the  chlorine  gas  has  reached  the 
pellets  and  completely  displaced  the  air  (why  ?),  heat  strongly 
with  a  blast-lamp.     Conduct  any  superfluous  chlorine  into  a 
test-tube  filled  with  sodium  hydroxide.     Describe  the  sub- 
stance which  is  formed  and  try  its  solubility  in  water  and 
acids. 

3.  CHROME-ALUM.     Dissolve  10  g.  potassium  dichromate 
in  water,  add  the  amount  (calculated)  of  sulphuric  acid  nec- 
essary to  form  potassium  sulphate  and  chromium  sulphate, 
warm  and  add  alcohol  (7  - 10  c.c.),  a  little  at  a  time,  until  the 
yellow  color  has  entirely  given  place  to  a  pure,  bright  green. 
The  action  takes  some  time  to  reach  completion.     Notice  the 
odor  (?).     Set  the  solution  aside  to  evaporate  spontaneously. 
Examine  the  form  and  color  of  the  crystals  when  they  appear. 
What  is  the  color  of  their  .solution  in  water? 

4.  CHROMATES.     Melt  5  g.  potassium  carbonate  with  equal 
amounts  of  potassium  hydroxide  and  potassium  nitrate  at  a 

101 


102  (CHROMIUM,  MANGANESE 

low  temperature  in  an  iron  crucible  and  stir  in  (use  the  reverse 
end  of  a  file)  5  g.  of  powdered  chromite.  Heat  strongly 
[Blast-lamp]  for  several  minutes  (?).  When  the  mass  has 
cooled  dissolve  it  in  a  little  boiling  water.  Add  dilute  nitric 
acid  until  the  solution  is  acid(?).  Note  the  change  in  color  (?). 

5.  CHROMIC  ACID.      Make  a  cold  saturated   solution  of 
sodium  dichromate,  add  it  to  two  volumes  of  concentrated 
sulphuric  acid  and  cool(?).     Filter  through  a  small  plug  of 
asbestos  and  dry  the  precipitate  by  smearing  it  on  a  piece  of 
broken  bisque  plate  [Storeroom]. 

6.  Take  some  potassium  dichromate  solution  and  run  into 
it  potassium  hydroxide  solution  from  a  burette  till  the  change 
in  color  is  complete.     A  test-tube  trial  will  show  the  tint  to  be 
reached.  Concentrate  the  solution  and  allow  it  to  crystallize  ( ?). 
What  kind  of  salt  (neutral,  acid,  basic,  double,  or  complex)  is 
potassium  dichromate  essentially? 

7.  REACTIONS  OF  CHROMIC  SALTS.  Use  diluted,  freshly  pre- 
pared chrome-alum  solution.     What  are  the  ions  in  the  solu- 
tion? 

a.  Boil  one  portion  of  the  solution  for  some  time  [R]  ? 
What  was  the  original  color  of  the  solution  ? 

b.  To  another  portion  add  sodium  hydroxide  solution,  at 
first  a  little  ( ?),  then  excess  ( ?).    Boil. 

c.  Add  colorless  ammonium  sulphide  (?).     Is  the  precipi- 
tate a  sulphide? 

d.  Add  excess  of  sodium  hydroxide  solution  and  then  a 
large  volume  of  bromine  water,  and  heat  ( ?).     Try  another 
portion  using  lead  dioxide  instead  of  bromine  ( ?)     Infer  the 
nature  of  the  action  from  the  change  in  color. 

8.  REACTION  OF  CHROMATES.     Use  diluted  potassium  chro- 
mate  solution.     What  are  the  ions  in  the  solution? 

a.  Acidify  the  solution  with  dilute  nitric  acid  ( ?). 

b.  Recall  the  actions  of  hydrogen  sulphide,  of  sulphur 
dioxide,  and  of  hydrogen  peroxide,  on  such  an  acid  solution  (?). 

c.  Add  colorless  ammonium  sulphide,  heat  and  maintain 
at  the  boiling  point,  noting  two  distinct  changes  (?),  then 
acidify(?). 

d.  Add  lead  nitrate  and  barium  chloride  to  separate  por- 
tions. 

9.  MANG ANGUS  AND  MANGANIC  SALTS.    Recall  the  prepara- 
tion of  a  manganous  salt  on  p.  30,  1,  b.  Name  a  manganic  salt. 
What  are  the  colors  of  their  solutions  and  therefore  of  the 


CHEOMIUM,  MANGANESE  103 

characteristic  ions  [R]  ?    The  chemical  actions  in  10  can  be 
followed  by  noting  the  changes  in  color. 

10.  MANGANATES  AND  PERMANGANATES. 

a.  Fuse  a  mixture  of  5  g.  of  potassium  hydroxide,  2.5  g. 
potassium  chlorate,   and   5  g.   finely  powdered   manganese 
dioxide  at  a  red  heat,  stirring  with  the  reverse  end  of  a  file, 
until  effervescence  ceases  (?).     Add  the  last  ingredient  grad- 
ually.   Treat  the  mass  with  a  small  amount  of  cold  water, 
decant  the  clear  liquid  away  from  the  precipitate,  and  use  it 
in  b,  c,  and  d. 

b.  Dilute  a  part  of  the  clear  green  solution,  with  a  very 
large  amount  of  water  in  a  beaker  (?).     If  no  change  should 
occur,  pass  carbon  dioxide  into  the  diluted  solution  ( ?). 

c.  To  a  portion  of  the  green  solution  add  a  few  drops  of 
alcohol  and  warm(?). 

d.  To  the  rest  of  the  green  solution  add  a  boiling  solution 
of  oxalic  acid  ( ?)  • 

e.  Repeat  c  and  d  with  potassium  permanganate  solution, 
acidified  by  adding  two  or  three  times  its  volume  of  dilute 
sulphuric  acid(?). 

/.  Add  similarly  acidified  permanganate  to  a  little  diluted 
ferrous  ammonium  sulphate  solution  till  the  pink  color  is 
permanent  (?).  To  the  product  add  ammonium  hydrox- 
ide (?).  What  change  has  taken  place  in  the  iron  (p.  69,  4,  c)? 

g.  Recall  the  action  of  the  same  reagent  on  hydrogen  sul- 
phide (p.  57,  3,  d)  and  on  sulphurous  acid  (p.  62,  9,  d). 

11.  REACTIONS  OF  MANGANOUS  SALTS.     Use  any  manganous 
salt. 

a.  Borax  bead  in  oxidizing  (?)  and  reducing  (?)  flames. 

b.  Bead  of  a  mixture  of  sodium  carbonate  and  sodium 
nitrate  on  a  platinum  wire  with  any  manganese  compound  (?). 

c.  To  a  diluted  solution  of  a  manganous  salt,  add  ammo- 
nium sulphide  ( ?).     Is  the  product  a  sulphide  ? 

d.  To  another  portion  add  sodium  hydroxide  (?).    Divide 
into  two  parts.     Shake  one  with  air(?).     To  the  other  add 
bromine  water  and  warm(?). 

12.  Apply  to  instructor  for  two  unknown  substances  and 
identify  them. 


CHAPTEK  XXV. 

IRON,    COBALT,    NICKEL. 

1.  IRON.     Recall  the  action  of  iron  on  dilute  acids  (p. 
22,  1,  a,  c,  d\  also  its  preparation  from  the  oxide  (p.  24,  5,  a). 

2.  FERRIC  SULPHATE. 

a.  Weigh  3.5  g.  of  concentrated  sulphuric  acid  into  an 
evaporating  dish,  add  20  g.  of  crystallized  ferrous  sulphate, 
and    dissolve    in    25-30  c.c.  of    water.      Heat  on   a  square 
of    wire   gauze   [Hood]    and   add   concentrated    nitric  acid 
drop  by  drop  till  the  color  of  the  solution,  dark  at  first  ( ?), 
changes  to  a  light  brown  (?  p.  69,  4,  c).     Evaporate  to  a 
syrup  on  the  steam  bath,  dissolve  tlie  residue  in  the  minimum 
amount  of  boiling  water,  add  3.5  g.  of  ammonium  sulphate, 
likewise  dissolved  in  the  minimum  amount  of  boiling  water, 
and  set  aside  to  crystallize.  Describe  the  crystals  ( ?).   Collect 
them  and  wash  them  free  from  the  mother  liquor,  dry  with 
filter  paper,  and  preserve  for  use  in  4. 

Chlorine,  bromine,  and  other  oxidizing  agents  have  the 
same  effect  as  the  nitric  acid  here  used.  With  what  other 
have  we  previously  produced  the  same  change? 

b.  Dissolve   some   ferric   sulphate   in   water.      Note   the 
color  (?)  and  reaction  of  the  solution  (?).     Add  some  pure  sul- 
phuric acid  (?).     Account  for  what  you  observe  and  explain 
the  behavior  of  the  salt  in  terms  of  the  ionic  theory. 

3.  SALTS  OF  COMPLEX  ACIDS.     Ferrocyanide  and  ferricya- 
nide  of  potassium.     Take  some  potassium  ferrocyanide  solu- 
tion in  a  test-tube  and  add  bromine  water  until  a  drop  of  the 
solution  gives  no  blue  precipitate  with  a  dilute  ferric  chloride 
solution.     What  does  the  solution  contain  [R]? 

4.  REACTIONS  OF  FERROUS  AND  FERRIC  SALTS. 

a.  Borax  bead  with  any  compound  of  iron  (the  oxide  or 
sulphate  is  best)  in  oxidizing  and  reducing  flames  ( ?). 

Examine  the  action  of  the  following  substances  on  a 
diluted  solution  of  ferrous  ammonium  sulphate  (freshly  pre- 
pared) and  on  a  diluted  solution  of  iron  alum  (made  in  2)  or 
ferric  chloride. 

b.  Test  the  effect  of  each  solution  on  litmus  paper  (?). 
Which  has  the  stronger  effect?     What  do  we  infer  (p.  94,  6) 

104 


IRON,  COBALT,  NICKEL  105 

from  this  ?    If  the  difference  is  not  plain,  try  paper  dipped  in 
u  Congo  red  "  [Storeroom]. 

c.  To  a  portion  of  each  solution  add  ammonium  hydrox- 
ide (?).    Note  the  effect  on  each  precipitate  of  shaking  with 
air(?). 

d.  To  another  pair  of  portions  add  ammonium  sulphide 
solution  (?)  [R].     Is  the  precipitate  soluble  in   hydrochloric 
acid?     How  could  you  prove  experimentally  that  free  sulphur 
is  formed  in  the  case  of  ferric  salts  ? 

e.  Potassium  ferrocyanide  solution  (?). 
/.  Potassium  ferricyanide  solution  (?). 

g.  Potassium  sulphocyanide  solution  (?). 

h.  The  reduction  (p.  58,  3,  e\  of  ferric  salts  in  solution  is 
as  easy  as  the  converse  operation  (2,  a).  Boil  a  little  diluted 
ferric  chloride  solution  with  a  pinch  of  powdered  iron  and 
test  a  drop  from  time  to  time  ( ?).  What  reagent  will  you  use 
in  testing? 

i.  Ascertain  experimentally  whether  solutions  of  ferro-  and 
ferricyanides  contain  a  detectable  proportion  of  iron  ions. 

k.  Show  that  the  crude  hydrochloric  acid  contains  ferric 
chloride  (?).  Show  that  the  same  substance  contains  sul- 
phuric acid  as  another  impurity.  (The  yellow  color  is  partly 
due  to  the  presence  of  an  organic  substance.) 

5.  REACTIONS  OF  SALTS  OF  COBALT.    Use  diluted  cobalt  chlo- 
ride solution. 

a.  Borax  bead  in  oxidizing  and  reducing  flames  (?). 

b.  Add  sodium  hydroxide  solution — first  a  little  (?),  then 
excess,  and  warm  ( ?). 

c.  Ammonium  sulphide  solution  (?). 

6.  REACTIONS  OF  SALTS  OF  NICKEL.     Use  diluted  nickel  sul- 
phate solution. 

a,  b,  c.  Same  as  in  5. 

7.  Obtain  two  unknown  substances  from  the  instructor 
and  identify  them. 


APPENDIX 


TENSION  OF  AQUEOUS  VAPOR  IN  MILLIMETERS. 


TEMP. 

0° 

5 

8 

9 
10 
11 
12 
13 
14 
15 


4.6 

6.5 

8.0 

8.6 

9.2 

9.8 

10.5 

11.2 

11.9 

12.7 


TEMP. 

PRESS. 

16° 

13.5 

17 

14.4 

18 

15.4 

19 

16.3 

20 

17.4 

21 

18.5 

22 

19.7 

23 

20.9 

24 

22.2 

25 

23.6 

TEMP. 

PRESS. 

26° 

25.1 

27 

26.5 

28 

28.1 

29 

29.8 

30 

31.5 

31 

33.4 

32 

35.4 

33 

37.4 

34 

39.6 

100 

760.0 

DEGREE  OF  IONIZATION  OF  ACIDS,  BASES  AND  SALTS. 

Except  where  otherwise  specified,  the  figures  give  the  per- 
centage ionized  in  a  normal  solution  at  18°,  calculated  from  the 
electrical  conductivities. 


ACIDS                PER  CENT. 

SALTS                PER  CENT. 

HNO3      .     .      .     82.0 

KC1     ....     75.0 

HNO3  (cone.,  62$)  9.6 

NH4C1    .    .      .     74.0 

HC1     ....    78.4 

NaCl     .     .        .    67.6 

HC1  (cone.,  35$)    13.6 

HgCl2  .     .    .     <    1.0 

HMnO4(N/2,25°)93.3 

KNO,  ....    64.0 

HI  (N/2,  25°)    .    90.1 

K8SO4      .     .     .    53.0 

HBr(N/2,  25°)      89.9 

K2C03      .     .    .   (49.0) 

H2FS    ....      7.0 

KClO,(N/2)     .    79.0 

H,SO4      ...    51. 

Na.HCO3      .     .   (52.0) 

H2SO4(conc.,95$)  0.7 

Na8C4H4O6(N/32, 

H.H,P04  (N/2, 

25°)      .     .     .   (78.0) 

25°)     .     .     .    17.0 

ZnSO4     .      .     .    24.0 

HC2H3O3     .    .      0.4 

Hg(CN)2  .     .      <    1.0 

HC2H3O8  (N/10)    1.3 

CaSO4(N/100)       63.0 

H.HCO3(N/10)       0.17 

H.HS(N/10)      .      0.07 

H.H2BO3(N/10;     0.01 

HNC(N/10)      .      0.01 

BASES 


PER  CENT. 


LiOH  .  . 
NaOH  .  . 
KOH  .  .  . 
Ba(OH)2  .  . 

Ca(OH)2(N/64, 

25°)       .     . 
Sr(OH)2(N/64, 

25°).    .     . 
Ba(OH)2(N/64, 

25°)      .     . 
AgOH(N/1783, 

25°)      .    .    . 
NH4OH 


63 
73 

77 


90 
93 
92 

38.! 
0, 


H.OH<lperlOmil. 


106 


APPENDIX  107 

SELECTION    FOR    STUDENTS    WITH    ADMISSION 
CREDIT    IN    CHEMISTRY 

CHAP.  CHAP. 

LI;  2;  3;  5;  6.  XIV.  1. 

III.  1,6;  2,  a  or  6.  XV.  1,  b,d;  2;3,6,c;  4;  5. 

IV.  4;  5;  6.  XVI.  2;  3,  b;  5;  6,  b;  8;  9; 
V.  2,  a;  3  a;  5  or  6  a  or  b;  7.  12;  13. 

VI.  1;2,  c,  d;  5.  XVII.  8,  6;  9,6. 

VII.  2;  3,  d;  6;  7.  XVIII.  1;  3. 

VIII.  1,  a,  3,  a,  6,  c.  XIX.  2;  3;  4;  6;  7;  8;  9. 

IX.  2;4,d.  XX.  3;  4;  5;  7. 

X.  l;2,a,  6,  d;  3,  a,  XXI.  1;  2;  6. 

4;  5;  6;  7;  8.  XXII.  1;  2;  3;  4;  5;  6;  7. 

XL  2;  3;  4;  5;  6;  7.  XXIII.  1;  2;  4;  6;  8;  10. 

XII.  1;  2,  d,  e;  3;  6;  7;  8;  XXIV.  1;  2;  4;  5;  9;  10. 

9;  10.  XXV.  3;  4;  7. 
XIII.  2,  c;  3;  4;  5,  c; 
9;  10;  11;  12. 

This  suggested  selection  of  laboratory  work  for  college 
students  who  have  admission  credit,  on  the  basis  of  a  year 
of  chemistry  in  a  secondary  school,  is  subject  to  further 
adaptation  to  individuals.  In  all  cases  the  student  will  be 
expected  to  master  the  topics  omitted  in  the  laboratory. 


